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Experiment: measure the speed of light with a laser.

Think it takes expensive, sophisticated equipment to measure light speed? Think again!

You can measure the speed of light using just a laser pointer and a container filled with gelatin.

EThamPhoto/The Image Bank/Getty Images

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By Science Buddies

July 8, 2024 at 6:30 am

Objective : Measure the speed of light in gelatin using a laser pointer

Areas of science : Physics

Difficulty : Easy advanced

Time required : 6–10 days

Prerequisites : Basic understanding of optics and trigonometry

Material availability : Readily available

Cost : $20–$50

Safety : Adult supervision is recommended. Even low-power lasers can cause permanent eye damage. Please carefully review and follow the  Laser Safety Guide .

Credits : Shijun Liu, Science Buddies; Harvey Lynch, Stanford Linear Accelerator Center (SLAC)

The  law of refraction ,  which is also known as  Snell’s law,  actually applies to everyday life. For example, when you see your friend’s face through the window, you’re seeing light that is refracted through the glass. Snell’s law describes what happens to the  trajectory  of a beam of light as it passes from one medium, such as air, to another, such as glass.

As you apply Snell’s law and the definition of  index of refraction  in this science project, you will be able to measure the speed of light in gelatin. The beauty of this science project also lies in how you can verify one of the most basic laws of optics, experimentally, by using readily available and inexpensive materials.

Snell’s law is expressed as the following equation (see Figure 1 below for an illustration of the variables):

Equation 1:

• θ 1  is the angle between the incident light beam and the surface normal
• θ 2  is the angle between the departing light beam and the surface normal
• v 1  is the speed of light in the first material (in this project, air)
• v 2  is the speed of light in the second material (in this project, gelatin)
• n 1  is the index of refraction of the first material (in this project, air)
• n 2  is the index of refraction of the second material (in this project, gelatin)

Note that Snell’s law not only applies to the case of the laser beam passing through air and gelatin, but also to other examples of how the  incident object  changes direction as it passes from a faster medium to a slower medium, and vice versa.

For example, a marching band walks together in time with the music and takes the same-length steps. What if the band moves across a grassy football field at an angle, and as each band member crosses the 50-yard line, he or she suddenly finds the field very muddy and slippery? As a result, he or she steps in time but takes steps that are 20 percent shorter because of the mud. What happens then? Answer: Those who have crossed the 50-yard line are traveling at 80 percent the speed of those who have not, and the line of band members bends at the 50-yard line, just like light in this experiment. With a little thought, one can even compute the  angle  at which the line bends (actually the reverse of what you will be trying to do in this science project).

Terms and concepts

• Law of refraction (also called  Snell’s law )
• Index of refraction
• Incident object
• What exactly  is  a laser?
• What is the speed of light? What are some methods scientists have used to calculate it?
• What are some applications of Snell’s law?

This resource provides more information about lasers:

• Wikipedia Contributors. (2010, July 6.) Laser.  Wikipedia: The Free Encyclopedia.  Retrieved July 12, 2010, from  http://en.wikipedia.org/w/index.php?title=Laser&oldid=371975776 .

To learn more about Snell’s law, try these links:

• Wolfram Research. (n.d.).  Snell’s Law.  Retrieved July 12, 2010, from  http://scienceworld.wolfram.com/physics/SnellsLaw.html .
• Kaiser, Peter K. (n.d.).  Snell’s Law.  Retrieved July 12, 2010, from  http://www.yorku.ca/eye/snell.htm .
• Nave, R. (n.d.).  Snell’s Law.  Retrieved July 12, 2010, from  http://hyperphysics.phy-astr.gsu.edu/hbase/geoopt/refr.html#c3 .
• The Physics Classroom. (n.d.).  The Mathematics of Refraction: Snell’s Law.  Retrieved July 12, 2010, from  http://www.physicsclassroom.com/Class/refrn/u14l2b.cfm .

The links below contain additional information about the index of refraction:

• Reed, R. (n.d.).  Refraction of light.  Retrieved July 12, 2010, from  http://interactagram.com/physics/optics/refraction/ .
• Wolfram Research. (n.d.).  Index of Refraction.  Retrieved July 12, 2010, from  http://scienceworld.wolfram.com/physics/IndexofRefraction.html .
• Nave, R. (n.d.).  Index of Refraction.  Retrieved July 12, 2010, from  http://hyperphysics.phy-astr.gsu.edu/hbase/geoopt/refr.html#c2 .

Materials and equipment

• Many kinds of lasers are readily available on the market. Typically, lasers are classified by their wavelength and maximum output power, which put them into one of several classes, e.g., class I, II, IIIa, IIIb, IV (see  Laser Safety Guide ). When handling lasers, please keep in mind the safety measures that must be followed in order to prevent injuries.
• A mounting device on which the laser device rests that can easily indicate where the beam is pointed (it will be difficult to actually see the laser beam passing through air).
• A protractor or a homemade protractor that can easily indicate the angle of refraction inside the gelatin.
• Gelatin (a clear or a light/transparent color generally works best).
• Plastic containers to mold the gelatin (of various shapes and sizes if pursuing one of the possible variations below).

Experimental procedure

Below is an outline of one way to carry out the experiment. There are multiple variations and points where you can insert your own creativity (see below):

1. First, come up with your own experimental setup. In addition to understanding the theory behind the experiment, this project calls for some experimental design creativity and hands-on “playing time.” Think about how one would measure the angle of incidence of a laser passing through the gelatin, with reference to the normal (the line that is perpendicular to the surface of the medium). Also consider how one could precisely direct the laser beam from the laser pointer (or laser level) at a predetermined “entry point.” What type of mounting structure would you come up with? For example, the photo below (using a tub of liquid instead of gelatin) represents a clever setup. The laser beam was originally along the line between the tiles on the countertop (you could also use graph paper). You can see a bit of the beam exiting the laser in the center of the circle, and you can see the entry point of the laser in the plastic container. These two points show the original path of the beam, and you can easily connect the points to create the original trajectory. (Note that the normal, which is not shown, is the line that runs perpendicular to the side of the plastic container that gets hit by the laser.) Thus, we can accurately measure the angle here.

2. Make your gelatin according to the directions on the box. Remove the gelatin from the container when it has set.

• Note:  Try to make the gelatin in a square container (like the container shown in the photo above). If a square container is not available, use a large container and cut the gelatin in a square or “box” shape with edges that are clean and vertical. Slanted and uneven edges may cause disruption of the laser beam, so it is important that the form of the gelatin be correct.
• Note:  The gelatin can be deformed if you are not careful when removing it from the container — or deformed by the tools you use to remove it. One way to remove the gelatin from the container is to set the container in hot water and let it float on the surface for a bit. This softens the edges of the gelatin inside the container, allowing you to turn the container upside-down to release the gelatin. Having the gelatin out of the container gives a clean optical interface, but gelatin may not stay straight once it is out of the mold. If the sides bulge significantly, the angles will be distorted.

3. Mount the laser pointer on a premade device that will indicate where the beam is going and what the angle of incidence is (recall that it will be difficult to actually see the laser beam passing through air).

• Note:  It is important that the laser beam be perpendicular to the surface for proper refraction results.

4. Fix the laser device and record the angle of incidence with respect to the normal.

5. Shine the laser through the gelatin. (You may need another person to help out by holding down the button if you use a simple laser pointer.) Measure the angle of refraction inside the gelatin.

• Note : Measuring the angle from the normal can be tricky. One must remember that if one looks directly into a refracting medium, i.e. , perpendicular to the surface, the angles are accurate, but if one looks off the normal, the angles are distorted. For example, a straight stick thrust into water looks broken at the surface. Therefore, it is important to set up the angle measuring device properly so accurate readings can be obtained.

6. Find the speed of light in gelatin: First, use Snell’s law (refer to the introduction) to calculate the index of refraction of the gelatin. Then apply the definition of index of refraction to find the speed of light in the medium.

There are many areas of this project where one can use their own creativity:

• Laser mounting device.  Make your own device to ensure that the laser beam precisely enters the gelatin at the predetermined entry point.
• Measuring scheme for the angle of refraction.  Design your own scheme to measure the angle of refraction inside the gelatin. For example, where would you place a custom-made protractor to indicate the angle of refraction with respect to the normal?
• Faster or slower gelatin.  Attempt to change the index of refraction of the gelatin and create “faster” or “slower” media. For example, what happens when one dissolves various amounts of sugar in a well-mixed gelatin solution? Does the index of refraction of the gelatin change? Consequently, how does the speed of light in gelatin change? Note that one can represent the concentration of the sugar-gelatin solution by doing a one-step percent composition by mass calculation, which is basically the mass of the solute divided by the mass of the solution (mass of solute plus mass of solvent), multiplied by 100.

For example: Determine the percent composition by mass of a 100 g salt solution which contains 20 g salt.

Solution: 20 g NaCl / 100 g solution x 100 = 20 percent NaCl solution

From the table shown below, we see that the index of refraction for a 30 percent sugar solution is 1.38 and for an 80 percent solution is 1.49. Can you verify a positively correlated trend for sugar?

• Other readily available materials.  Calculate and verify the indices of refraction of other readily available materials like household liquids or ice. For example, ethyl alcohol has an index of refraction of 1.36, while ice’s is 1.31. Can you verify this? A table of indices of refraction for commonly found materials is shown below. Note that extra caution must be taken if you are using a plastic container to hold the liquid as the container itself serves as an interface between the laser and the media. Think about ways to minimize this distortion. For example, can you try to aim the laser at the surface of the liquid (at an angle with respect to the normal) from above? How would you measure the angle?
• Make lens cross-sections out of gelatin, then “ray trace” with the laser.  Basically, ray tracing involves establishing the position and orientation of an object’s image by tracing strategic rays of light from the object passing through the lens, using knowledge of the focal length of the lens and the position of the object. Here is an introduction:  http://boson.physics.sc.edu/~rjones/phys153/raytrace.html .

This activity is brought to you in partnership with  Science Buddies . Find the original activity  on the Science Buddies website.

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Laser Jello

Gelatin can be used for much more than a sweet treat. It can also act as a smoked lens—which allows you to view total internal reflection—or as a color filter.

• Petri dishes
• Square, open-topped boxes made of clear plastic
• Two packages of Jello®—one red and one blue
• Package of clear gelatin (Knox® brand is easy to find in supermarkets)
• Red and green laser pointers
• A protractor

• Prepare the red, blue, and clear gelatin according to the Jello Jigglers™ recipe (found on the Jello® boxes).
• Pour about 1/2 inch (1.25 centimeters) of blue gelatin into a round Petri dish.
• Pour about 1/2 in (1.25 cm) of red gelatin into a round Petri dish and 1/2 in (1.25 cm) into a square container.
• Pour about 1/2 in (1.25 cm) of clear gelatin into a square container.   

Hold the red laser flat against the table so the light beam is parallel to the table. Shine the laser through the middle of the round dish of red gelatin—a beautifully visible beam travels through it. Then shine the laser through the blue gelatin. Notice that the beam gets dimmer almost as soon as it hits the gelatin. Shine the laser through the dish of clear gelatin. Notice that you can see the beam very clearly

Shine the green laser through the round dish of blue jello and observe the beam as it travels through the jello. Shine the green laser through the red jello and notice that the beam gets dimmer as soon as it enters the jello.

Hold the laser parallel to the table and shine it through one side of a square dish of red or clear gelatin. (Use the red laser for the red gelatin; use either the green or red laser for the clear gelatin.) Start with the beam perpendicular to the edge; notice that it passes through the gelatin in a straight line. Now rotate the laser so that the beam hits the flat edge of the dish at an angle. As you do so, notice how the beam bends towards the center of the dish. Use the protractor to measure the angle of incidence between the beam and a line perpendicular to the flat edge, and the angle of refraction after it enters the gelatin.

Next, take the round Petri dish of blue gelatin. Holding the green laser parallel against the tabletop, shine the laser through the middle of the curved edge of the dish (it should look as though the laser is bisecting the circle). Now, starting from the laser's original position, slide the laser in a straight line to the right and then the left, so that the beam moves toward the outer edges of the dish. Notice how, as you do so, the beam bends towards the center of the dish. (Note: Hold your two lasers parallel to one another and shine both beams through the curved edge of the dish, and then use a piece of white paper or waxed paper as a screen to find the focal point where the two beams cross—see the What's Going On? section below for more information.)

Finally, take a square dish of red or clear gelatin. Holding either laser parallel to the table (use the red laser for the red gelatin; use either the red or the green for the clear gelatin), shine the beam through one edge of the box and notice the beam coming out the far side. Now, shine the beam through one side of the box so that it hits the adjacent side at a glancing angle—you'll notice that no light exits the box through that side! (You may need to play around a bit to find the right glancing angle.) The largest angle at which no light escapes is called the critical angle .

Gelatin is colloidal—its large molecules are suspended in solution in such a way that they don't settle out—and so it scatters enough of the laser beam to make it visible. Red dye in the red gelatin doesn't absorb red light, so you can see the red beam when it shines through it. The blue gelatin (which is actually cyan) absorbs red light (but not blue or green), so the red beam isn't visible.

As light enters the gelatin, the change in medium causes a change in the speed of the light and a change in the index of refraction. This change in speed causes the direction of the beam to refract , or bend. When going from a high-speed material such as air to a lower-speed material such as gelatin, the beam will bend into, or towards, the gelatin.

Light traveling through a convex lens will converge. If you shined two parallel beams through your gelatin, you saw that parallel beams of light will come together at a point on the far side of a curved lens (in this case, the curved side of the dish)—this is called the focal point . (Teachers! This might be a good time to introduce the reversibility of light. Shine a laser through your gelatin "lens"—mark its path into and then out of the gelatin. Shine a laser backwards along this path—that is, shine it into the path that the original beam exited. The light path followed by the reversed beam will be exactly the same.)

As light travels from a slower (or more optically dense) substance to a faster medium, it may reflect in a similar way to the skimming of a stone off the surface of water. If the beam hits at an angle that is small relative to the surface, then the light will completely reflect—this is called total internal reflection . If the angle is closer to perpendicular, then the beam will exit out the side of the dish.

As it moves from a higher-speed medium to a lower-speed one, a ray of light will behave similarly to the way a car behaves as it moves from paved asphalt to soft dirt or loose gravel. The car will change direction by angling into the gravel, the same way a beam of light will refract by turning in a similar direction towards the lower-speed material.

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Bend A Laser Beam With This Easy, Physics-Defying Experiment

By Thom Leavy

Posted on Oct 6, 2016 5:19 PM EDT

Want to defy physics? This experiment makes a straight laser beam appear to bend into a curve.

Fasten a laser pointer to a flat surface, positioned so it shines horizontally through a full plastic water bottle. Poke a hole in the plastic where the beam of light exits; water will spill out in an arc. (Use a bowl to catch the runoff.) The laser light will appear to bend along with the water. How is this possible?

According to Snell’s law, a ray of light will change its angle when it hits the boundary between one medium (water) and another (air). So the light is actually bouncing back and forth in straight lines within the stream of water, as if trapped in a hall of mirrors.

This article was originally published in the September/October 2016 issue of Popular Science, under the title “Bend a Laser Beam.”

Simple Laser Diffraction Experiment at Home

Introduction: Simple Laser Diffraction Experiment at Home

Long story short : You will learn how to observe interference patterns at home (using the cheapest laser point you got). I will also teach you how to use your laser to measure tiny objects, like the width of your hair !! It's super easy!

* This instructable can seem a bit technical, so feel free to ask me stuff!

If you find physics interesting I suggest you read through (at least the introduction part!) before you skip to the pictures and videos and how-to's!

Long story starts here:

So interference patterns look cool, but so are many other things!! why should we study them??

As a physicist you get to study how things work. You start with the basics - mechanics (Newton and his buddies from the 18th century), and gradually move towards the 19th century where you learn about electro-magnetism (Maxwell and such) and eventually you get to Quantum Mechanics and Einsteins relativity. There are many universalities to these theories, but my favorite is that they can all describe waves.

Whether it's the waves on the surface of a pond or a vibrating string which are usually described by Newtons laws, light, which is an electromagnetic wave, gravity waves described by Einsteins theory, or miniature particles described by wave mechanics (aka Quantum Mechanics) - they all share many similar properties.

This makes the study of waves an extremely important part of the education of physicists. In my opinion, it helps you develop intuition and see the world differently. Once you study what waves are, you begin to see them everywhere.. and it's beautiful! One of my favorite wave phenomena are related to wave interference, which lead to interference patterns.

To perform the single-slit experiment at home, you'll need:

1) 2 old credit-cards (or some more plastic cards). I painted mine with a dark permanent marker

2) A piece of plywood (about 1/2 inch thick).

3) 2 short flat-end screws (about 1/2 inch long).

4) 2 longer flat-end screws (about 2 inches long) and suitable nuts.

5) Rubber bands

6) 6 small right-angle joints (see picture)

7) a laser pointer

Step 1: What Are Interference Patterns?

We all know what waves are from our everyday lives, but what are they, really?

Waves are disturbances to a "field". In the case of sound waves, for example, this "field" is the air-pressure around us - sound waves are simply disturbances to the air pressure that travel through space. For our purposes, we should consider a simple case where these waves are periodic in time.

I added a video from Veritasium's channel that talks about waves. It's a nice video that should teach you the basics of waves.

Now, imagine two identical waves travelling through space. When these two wave collide with, they add up to form a single disturbance. Many waves are even simpler than that - the magnitude of the combined oscillation is simply the sum of both waves.

There are two interesting cases to talk about. If both waves happen to meet at a point in space while both oscillations are at their maximum, the wave we would see when we look at it would be a single wave, with twice the magnitude of each one separately. This is called constructive interference . Alternatively, if the two waves meet at a point in space while one is pointing 'upwards', while the other is pointing 'downwards' (one is positive and the other is negative), they completely cancel each other out! This is called destructive interference .

An interference pattern is what you get when you look at more than one point in space. For example, if you throw two rocks into a pond, their ripples would interfere with each other in many places - in some points they would interfere constructively and in others they would interfere destructively.

Step 2: The Single Slit Experiment

Light, as it turns out, is also a wave (it is a disturbance in the electromagnetic field). This means that light beams can also interfere with each other! There are many ways to see this, but one of the simplest experiments is the single-slit experiment.

When a light-beam (a wave) hits a narrow slit, it shatters in many directions. Each point of the slit would behave a source for new waves, which could interfere with each other. If we now place a piece of paper a few feet away from it, we would see the resulting interference pattern!

This pattern can be predicted from the physics theory of waves. In our case, it is only interesting to quote the final results, which is called a "sinc" function (see the image I attached). The cool part is that this pattern can tell us stuff! For example, if we know the width of the slit, and the distance from the slit to our piece of paper, we can calculate the wavelength (~the period) of the light-wave we used! If, on the other hand, we know the type of laser we used, we can measure the width of tiny objects using the simplest laser-point we got!

But more about this later, for now, let's first see how to observe this pattern using a cheap laser-pointer.

Step 3: Assemble the Experiment

First, attach two short flat-head screws and a right-angle joint to one of the plastic cards (see first picture). On the other side, attach another right-angle joint (see 2nd and 3rd picture). Notice their orientation. Similarly, attach right-angle joints to the other plastic card so that they face each other (see 4th image).

Next, fix one of the plastic cards to the plywood. Now use two more right-angle joints such that they form a track pointing at the previous (fixed) card. This will allow the 2nd card to slide towards the first (fixed) one. Attach these joints to the plywood (see picture 4).

You should now have one fixed plastic card and another that can slide towards it.

Finally, screw in a long screw to the plywood next to the sliding card (pointing upwards), and connect it with rubber bands (see pictures 4-5). Connect the two cards using long flat-head screws. When you screw the them in, the cards should come closer to each other, and when you unscrew them, the cards should move apart.

I also added a small stand for the laser-pointer with rubber bands holding it to place (see last image). When I turn the laser on, the beam hits the slit formed between the two cards (see last picture). When I move the cards close to each other, a diffraction patter is formed!

Step 4: Single-Slit Experiment

Safety First

Laser pointers, of any kind, can damage your sight! do not point them at anyone's eyes or at any reflective surfaces. The cheapest lasers often have a much higher potential for damaging your eyes!

Performing the Experiment

Place your laser + slit at a given distance away from a white wall. About 2-4 feet away should be fine.

Turn on the laser and displace the move-able card such that the laser beam passes through without hitting the plastic cards.

Now, using a screwdriver, slowly bring the two plastic cards closer together such that a narrow slit is formed between them. Notice what happens on the wall! As you bring the cards closer to each other, the interference pattern on the wall becomes larger and larger!!

In the video you can see what it should look like when you change the width of the slit back in forth. I also took a picture with my phone and analysed the light intensity (gray-scale) using a free software called imageJ . Notice how it very much resembles the 'sinc' function I mentioned earlier!

Step 5: Using Laser to Measure Tiny (microscopic) Objects

How can we use this interference patter to measure microscopic objects?

When sizes are larger than, say, a millimetre, you can use ordinary tools such as a ruler or a caliber to measure them. But when you reach the micrometer scale, things get more complicated (at least at home!). For example, a human hair is about 100 micro-meter thick, and it's not that easy to measure it using everyday tools!

We can overcome this using a cheap laser pointer! It turns out that if you know the wavelength of the laser you're using (red lasers are usually ~630-670 nano-meters, 650nm would be a good approximation) and the distance between your object (in our case, the slit) to the wall, you can calculate the size of that object!

All we need to do is measure the distance between the central lobe (the bright spot in the middle) to the next bright spot. Let's denote this distance by the letter 'y'.

The image is taken from hyperphysics . Let's use their notation. If we denote the size of the object we're measuring by the letter 'a', the distance from that object to the wall by 'D' and the wavelength by the Greek letter 'lambda'. Using these notations, the size of the object is given by:

a = 3/2 * lambda * D / y

In the image they have decided to measure the distance from the first lobe to the following dark spots - you can can even use their calculator to plug in the measurements you took in order to calculate the size of the object you've measured.

But this is just a slit, how can we use this to measure other objects?

It turns out that if you take other objects which are narrow enough, such as a human hair, the resulting diffraction pattern will be very similar (and often identical) to the single-slit experiment! This means that the same formula I showed you earlier works just as well!

So.. if you want to measure tiny objects, just shine a laser beam at them, and analyse their diffraction pattern!

If you want to see this happens, just t ake a single human hair and hold it against your laser pointer. This will create a diffraction pattern which you can use to measure the width of your hair ! I used this and found that my hair is about 100 micrometers thick!

That's all for today! see you soon :)

To revisit this article, visit My Profile, then View saved stories .

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Diffraction of laser light

Class demonstration

This demonstration shows that a beam of light is diffracted as it passes around a wire, highlighting the wave nature of light.

Apparatus and Materials

• Laser source
• Thin, straight wire, approx 25 cm
• Stand with 2 clamps

Health & Safety and Technical Notes

Read our standard health & safety guidance

You will probably need to work in a darkened room.

Care should be taken to ensure that the laser beam does not shine directly into students’ eyes. This can be avoided by fixing it firmly in a clamp directed away from the students and towards the screen. Ensure that there are no shiny, reflective objects close to the path of the beam.

• Mount the laser pointer horizontally in a clamp
• Mount the wire vertically between two clamps.
• Direct the laser light onto the screen. You will see a bright dot.
• As suggested in the film, ask your students to predict what they will se when the wire partially blocks the laser beam.
• Move the wire into the beam. You should see a diffraction pattern of light and dark ‘fringes’ on the screen.

Teaching Notes

• We may talk casually about ‘light waves’, but students need to be convinced that light travels as a wave. This demonstration shows it.
• Students will need to be familiar with two ideas: that waves diffract as they pass around an obstacle, and that waves interfere constructively and destructively when they overlap. These ideas can be shown using a ripple tank.
• You can show diffraction and interference of light using single, double or multiple slits. However, students may find these difficult to appreciate. Diffraction by a simple wire is a more straightforward situation to explain. Students can also be asked to predict what will be seen on the screen when the wire is placed in the path of the light beam. They will probably expect to see a vertical shadow. The appearance of a diffraction pattern spread across the screen is a surprise worth exploring.
• A laser is used because it is a convenient source of a narrow beam of light. It has the added advantage that it produces light of a single wavelength; white light would produce a similar effect but the diffraction pattern would not be as wide as different wavelengths (colours) would interfere at different points.
• It is worth emphasising the extent to which light is diffracted as it passes around the wire. The diffraction pattern may be 50 cm wide when the diffracting wire is one metre from the screen. So light is being diffracted (bent) through an appreciable angle – perhaps 20 degrees.
• You could investigate the effect of rotating the wire; can students predict what will happen? (A vertical wire produces a horizontal diffraction pattern; a horizontal wire will produce a vertical pattern.)

diffraction of light collection

• The video shows how to demonstrate the diffraction of light using a laser pointer and a wire:

• This video can be used with your students in the classroom in place of the actual demonstration:

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Science project, diffraction grating experiment: wavelength of laser light.

Light propagates, or travels, in waves. Waves have two main properties: frequency and wavelength . When you know one, it’s pretty easy to calculate the other.

When light waves overlap they create interference, and the patterns caused by this can be used to determine the wavelength of light. Conduct this cool diffraction grating experiment to determine the wavelength of laser light emitted from any laser pointer.

Calculate the wavelength of light.

• Diffraction grating with lines of known separation
• Laser pointer with a known wavelength
• Meter stick
• Binder clips
• Tape an index card to the wall so the blank side is facing you.
• Lay the meter stick on a table or the floor so the 0 meets the index card.
• Mount the later pointer at the end of the meter stick, pointing towards the index card.
• Mount the diffraction grating a few centimeters from the index card so the lines are vertical.
• Turn off the lights in the room and turn on the laser pointer.
• Use your protractor to measure the angle between the meter stick and the first order visible band.
• Use the formula Where λ is the wavelength, in meters d is the distance in meters between lines on the diffraction grating θ is the angle and n is the order. Unless the room is extremely dark, you will only be able to see the first order, so n=1.
• Compare your calculated wavelength to the wavelength provided by the manufacturer of the laser.
• Repeat for different lengths along the meter stick.

Diffraction gratings diffract, or split, light periodically , meaning the light splits into several beams with a given angular separation. In this experiment, the first period , n=1, will be the brightest spot on the index card (besides the straight path of the laser, of course) after the grating splits the rays from the laser pointer. Using the formula above, you can verify the wavelength of light using what the manufacturer of the laser pointer says it is. If the room is dark enough, you may even be able to measure the 2 nd and 3 rd periods and plug n = 2 and n = 3 into your equation, respectively. It should yield the same result.

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How to Make Light Bend for Science Experiments

Last Updated: March 4, 2023 References

This article was co-authored by Bess Ruff, MA and by wikiHow staff writer, Hunter Rising . Bess Ruff is a Geography PhD student at Florida State University. She received her MA in Environmental Science and Management from the University of California, Santa Barbara in 2016. She has conducted survey work for marine spatial planning projects in the Caribbean and provided research support as a graduate fellow for the Sustainable Fisheries Group. There are 8 references cited in this article, which can be found at the bottom of the page. This article has been viewed 28,600 times.

When light slows down or is refracted through another material, it may appear to bend rather than travel in a straight line. Using only a few materials, you can demonstrate how light can be bent. You can use a water bottle, shoebox, or fish tank to demonstrate the laws of refraction and learn how light acts!

Bending Light with a Water Bottle

• If you have trouble piercing the bottle with the screwdriver, start the hole with an X-acto knife before forcing the screwdriver through the plastic.
• Ask a parent or adult to help you poke the hole if you’re under 10.
• Do the experiment over the sink if you don’t want to use another dish.

• Turn off the lights in the room you’re conducting the experiment to see the laser light better.
• Do not point a laser in anyone's eyes. This could cause permanent damage to their vision.
• This phenomenon is known as internal reflection.

Refracting Light in a Shoebox

• Ask an adult to help you with the knife if you are under 10 years old or uncomfortable using a knife.
• Colored film can be purchased at your local arts and crafts store.
• You can cover either the right or left slit.
• You only need to do this step if you want to see 2 different colors of light inside the box.
• Turn off the lights in the room so you can see how the flashlight works inside the box.
• Use a cylindrical-shaped glass for the best results. The width of the glass should be the same along its entire length.
• This occurs because the light slows down as it passes through the water, causing the beams to refract and bend.

Using Sugar Water to Bend Light

• Purchase white granulated sugar from your local grocery store.
• Use a cardboard tube to help direct the water more.

• Don’t stir the water or else the concentrations won’t settle evenly.
• Sugar water is denser than tap water, so it sinks below the water. The different concentrations affect how fast or slow the light moves through it, causing the laser to bend.
• Try the experiment with various colored laser pointers. Since the wavelengths are different with each color, the light will bend either sooner or later.

Community Q&A

• Keep a notebook with notes and drawings of your observations. Thanks Helpful 0 Not Helpful 0

• Don’t aim laser pointers into anyone’s eyes since this could cause damage to their vision. Thanks Helpful 0 Not Helpful 0
• Ask an adult to help you use utility or X-acto knives if you’re 10 or under. Thanks Helpful 0 Not Helpful 0

Things You’ll Need

• Empty water bottle - 16.9 fluid ounces (500 mL) or 20 fluid ounces (590 mL)
• Screwdriver or Exacto knife
• Laser pointer
• Cooking pan
• Utility or Exacto knife
• Transparent colored plastic
• Glass of water
• Rectangular 5 US gal (19 L) fish tank

You Might Also Like

• ↑ https://youtu.be/ifbCsha7Syc?t=41s
• ↑ https://youtu.be/ifbCsha7Syc?t=54s
• ↑ https://youtu.be/ifbCsha7Syc?t=1m9s
• ↑ https://www.wired.com/2011/01/simple-science-bending-light-with-water/
• ↑ https://youtu.be/sibPEma8nEM?t=2m27s
• ↑ https://youtu.be/sibPEma8nEM?t=2m49s
• ↑ https://youtu.be/sibPEma8nEM?t=3m9s
• ↑ https://youtu.be/sibPEma8nEM?t=3m38s

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The North Ossetia - Alania Republic, Russia

The capital city of North Ossetia republic: Vladikavkaz .

The North Ossetia - Alania Republic - Overview

The Republic of North Ossetia - Alania is a federal subject of Russia located on the northern slope of the Greater Caucasus, part of the North Caucasian Federal District. Vladikavkaz is the capital city of the region.

The population of the North Ossetia - Alania Republic is about 688,100 (2022), the area - 7,987 sq. km.

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North ossetia republic map, russia, north ossetia republic latest news and posts from our blog:.

13 April, 2021 / Mountain Landscapes of the Republic of North Ossetia - Alania .

6 October, 2020 / The City of the Dead in Dargavs .

26 June, 2018 / Beauty of Mountainous Digoria in North Ossetia .

28 May, 2016 / Stunning nature of the Caucasus - climbing Stolovaya Mountain .

History of the North Ossetia - Alania Republic

From the first millennium BC, Koban culture was spread on the territory of present North Ossetia. It was named after the village of Koban located in Tagaur canyon, where ancient archaeological monuments were found. Since the 7th century BC, the Scythian tribes began to settle in the Central Caucasus.

Koban population assimilated among the Scythians and then the Sarmatians, some of whom switched to a settled agricultural economy. By the 2nd century AD, the Sarmatians of South-Eastern Europe and Central Asia united under a new name - the Alans. Like the Scythians, the Alans used Derbent pass and the passes of the Greater Caucasus for their raids.

In 372, the nomadic tribes of the Huns invaded Europe from Central Asia. This invasion was the reason of migration of the Alans to the most inaccessible mountain areas on both slopes of the Greater Caucasus mountain range. In the 6th-7th centuries, Alania was again a relatively powerful state with a dense network of well-fortified settlements, developed agriculture, trade and crafts. At the beginning of the 10th century, Orthodoxy became the state religion in Alania.

In the 12th century, Alania experienced the feudal period and was divided into principalities fighting against each other. They were unable to unite against the Mongols who invaded the region in the 13th century. In 1222, the Mongolian army defeated the Alanian army. In January 1239, after a three-month siege, the Alanian capital of Magas was captured. The Mongols ravaged the plain part of the country, but the resistance continued in the mountain areas.

More Historical Facts…

The final blow in a series of tragic events of the 13th-14th centuries was the invasion of the troops of Tamerlane in 1395. Almost all of the Alans were killed, the state of the Alans collapsed. The survivors took refuge in the mountains where they mingled with the local population of other language group and later became known as the Ossetians.

In the 15th-17th centuries, the Ossetians fought for survival in extremely cramped conditions of the mountains (the plain was occupied by Adygeyan tribes). In the 18th century, the Ossetians were in need for resettlement on the plane because of the extreme shortage of land. Ossetia was also important for Russia, as the region that controlled the strategic passes in the Caucasus.

In 1774, the territory of North Ossetia was among the first regions in the North Caucasus, which joined the Russian Empire. Vladikavkaz, founded in 1784, became the first Russian fortress in the area. In the 19th century, the Ossetians migrated from the mountains to the plains and outskirts of Mozdok.

In Soviet times, Ossetia was divided into two parts. The part north of the Caucasian ridge came under the jurisdiction of the RSFSR (present Russian Federation), the part to the south came under control of the Georgian SSR. In 1921, Ossetia became part of Gorskaya Soviet Republic. It received the status of an autonomous oblast in 1924. In 1936, it was reformed into North Ossetian Soviet Socialist Republic.

During the Second World War, fierce battles took place on the territory of the republic, the northern and western parts of North Ossetia were occupied by the Germans. In November, 1942, the German advance was stopped near Ordzhonikidze (Vladikavkaz). About 85,000 people were drafted into the Soviet Army in the republic and almost 45,000 of them were killed.

During the war, the territory inhabited by the Ingush, who were deported for “collaboration” with the Germans, was joined to North Ossetia. Empty villages were inhabited by the Ossetians from North Ossetia, the South Ossetian Autonomous District and inner districts of the Georgian SSR.

The Ingush, who returned home in the 1950s, were given back part of their former territory. Instead of Prigorodny district, which then belonged to North Ossetia, they received the land taken from Stavropol krai. But the Ingush demanded that the eastern part of Prigorodny district should be returned to them. In 1992, an armed conflict broke out because of territorial disputes.

In 1993, the region received a new name - the Republic of North Ossetia. In January 1995, it received its present name - the Republic of North Ossetia - Alania.

In the 1990s and in the early 21st century, several major terrorist attacks occurred on the territory of the republic related to the wars in Chechnya including the taking of hostages in the school #1 in Beslan in 2004. This terrorist act led to serious political consequences not only for the republic but also for Russia in general (the system of election of regional governors was abolished).

North Ossetia - Features

The territory of the Republic of North Ossetia - Alania stretches from north to south for 120 km, from west to east - 125 km. The highest peak is Mount Kazbek (5,033 meters). The Terek is the main river.

It is one of the most densely populated Russian regions. About half of the population lives in Vladikavkaz. The largest cities and towns are Vladikavkaz (298,800), Mozdok (41,000), Beslan (37,300), Alagir (19,400), Ardon (19,200). The national composition according to the 2010 census: Ossetians (64.5%), Russians (20.6%), Ingush (4.0%), Armenians (2.3%), Kumyks (2.3%), Georgians (1.3%).

The climate is moderately continental in the central part and foothills. The average temperature in January is about minus 3.2 degrees Celsius, in July - plus 20.4 degrees Celsius. The natural resources of the region include complex ores containing zinc, lead, copper, silver, dolomites, mineral water springs. Also there are several oil deposits. Forests cover about 22% of the territory.

The main industries of the republic are non-ferrous metallurgy, machine-building, mining (non-ferrous ores, construction materials), electronics, light, glass, food. Several large plants producing spirits are located in Vladikavkaz and Beslan.

Two main highways (Georgian Military Road and Transkam) pass through the territory of North Ossetia connecting Russia with the South Caucasus countries and the Middle East.

Tourism in North Ossetia - Alania

Since the middle of the 19th century, Ossetia was positioned as one of the tourist centers in the North Caucasus. The Soviet period was the next milestone in the development of a recreational complex of the republic. By the early 1990s, spa treatment and tourist-excursion services became an important part of the local economy.

Today, North Ossetia may serve as a basis for the creation of a large health resort agglomeration, comparable to well-known Sochi-Matsesta and the Caucasian Mineral Waters regions.

The geographical location of the republic allows to organize year-round ski resorts. In addition to traditional forms of recreation, there is great potential for the development of extreme forms of recreation, agricultural and ecological tourism. North Ossetian State Nature Reserve is located in the upper reaches of the Tsey, Ardon and Fiagdon rivers.

The rich historical heritage of North Ossetia is of great value. The republic has more than 1,500 historical and cultural monuments. Vladikavkaz trams are one of the oldest tram systems in Russia (1904).

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Vladikavkaz, Russia

Tours, Attractions and Things To Do in Vladikavkaz

Vladikavkaz travel guide.

• 2. Architecture
• 3. Museums and Theaters
• 4. Outdoor Attractions
• 5. Souvenirs

Hospitable and sunny Vladikavkaz, the capital of Russia’s Republic of North Ossetia-Alania, captures the heart with its colorful mountain landscapes, historic architecture, kind residents and vibrant local culture.

The city is located on the banks of the Terek River and is almost completely surrounded by mountains which, along with unique Northern Caucasian architecture, make this urban landscape rather irresistible. Upon arrival, luxurious mansions, unusual architecture, parks, museums, theaters, retro trams and cozy eateries serving famous Ossetian meat pies all clamber for visitors’ attention, often pulling them back for further visits.

As the largest city in Russia’s southern Caucasus, Vladikavkaz is the start and ending point for many regional tourist routes, so after enjoying the city sites be sure to continue onward to the surrounding natural attractions .

History of Vladikavkaz

Vladikavkaz Fortress was built in 1784 to provide protection for the Russian Empire along its southern border with Georgia. The name Vladikavkaz means “I own the Caucasus” and was chosen by Catherine the Great after the Russian Empire extended its power into the region. The fort served a vital protective role for many years even as wealthy merchants and retirees began investing in the region’s development, and in 1860 Vladikavkaz attained the status of city. Later in the 19th century, newly laid rail lines in the region led to an economic boom and to an influx of ethnic minorities whose diverse houses of worship and unique architecture can still be seen in the city today.

Vladikavkaz was awarded the title of City of Military Glory after successfully fighting off invading Nazis in World War II. Today it remains an ethnically diverse city with hundreds of Art Noveau and historic buildings. Although no longer a military outpost, Vladikavkaz remains a soulful city with a rich cultural life . Read more...

Vladikavkaz Architecture

The city of Vladikavkaz is famous for its architecture, and for good reason. The city grew rapidly between the second half of the 19th century and the early 20th century due to the influx of high-ranking retired military personnel who built mansions and summer houses with their hefty pensions. It is believed that the presence of around 75 such individuals led to Vladikavkaz’s historic nickname "City of retired generals".

Today the historic city center is a chain of cozy avenues lined with many of these elegant mansions.

Prospekt Mira

Prospekt Mira (Mira Avenue) in Vladikavkaz is a kilometer-long boulevard which serves as the main pedestrian thoroughfare for the historic city center. It promises a pleasant walk amid slender two- and three-story merchants’ mansions, inviting coffee shops and other convenient photo opps.

Mukhtarov Mosque

Mukhtarov Mosque , also called Sunni Mosque, is an unmistakable landmark of Vladikavkaz. This delicately carved structure appears to have been lifted from the pages of a fairy tale and is often likened to Cairo mosques of the 10th-12th centuries. Built in the early 20th century, it remains an active mosque to this day.

Imperial Hotel

The main hotel in Vladikavkaz, Imperial Hotel on Mira Avenue has long been a city symbol. The fashionable accommodation was built in 1896, and although there were already 16 hotels in Vladikavkaz at the time, it quickly rose to prominence as the hotel of choice for the city’s most honored guests.

Other famous buildings in central Vladikavkaz include:

• Oganov Mansion (12 Mira Avenue)
• Mansion of the Lawyer Boehme (Pavlovsky Lane)
• Yastremsky Mansion (33 Sovetov Street)
• Khudyakovs’ Mansion (11 Mira Avenue)
• English Consulate Building (31 Lenin Street)

As you walk through the center of Vladikavkaz, you cannot miss these unique Northern Caucasian structures which preserve the memory of a bygone era .

Museums and Theaters

Many travelers who come to North Ossetia either visit Vladikavkaz in transit or skip it altogether in their rush to reach the Caucasus Mountains. However, it is here that life can be experienced in full swing and many options for leisurely activities can be found. Museums, theaters, cinemas, concert halls, parks and family entertainment venue all await you in Vladikavkaz.

At Opera and Ballet Theater , one of the largest musical theaters in the Republic of North Ossetia-Alania, you can enjoy quality opera and ballet performances by professional dancers, singers and musicians.

Vakhtangov Theater is another large public theater that offers performances for both adult audiences and young viewers. The theater opened in 1871 to host performances produced by outstanding Russian playwrights, including an early performance of "Masquerade" by Mikhail Lermontov. Mikhail Bulgakov staged his earliest plays at Vakhtangov Theater, which regularly hosts renowned Russian actors and theatrical figures to this day.

Narty Horse Theater offers highly unusual performances which combine elements of choreography and circus art subtly interwoven with a dramatic plot. This performance will definitely appeal to family members of all ages!

At the North Ossetian Philharmonic , exemplary performances by an all-male choir are held regularly.

National Museum of the Republic of North Ossetia-Alania is a museum, research center and exhibition complex with several branches, the main one of which is located in the city center at 11 Mira Avenue. Come get acquainted with a variety of historical findings which date back centuries. In total, the museum complex houses more than 4,000 exhibits which shed light on the history of the region and the peculiarities of the local culture.

M. S. Tuganov Art Museum , located at 12 Mira Avenue next to National Museum of the Republic, has amassed a large collection of works of fine art, including pieces by Levitan, Aivazovsky, Repin, Bryullov, Vereshchagin, Shishkin, Korovin and other acclaimed artists.

21st-Century Entertainment

As in any other major city in Russia, Vladikavkaz is home to a whole host of modern entertainment venues, including quests, laser clubs, time cafes and more .

Outdoor Vladikavkaz Attractions

While there are plenty of manmade attractions to see in Vladikavkaz, outdoor adventures also await travelers, both beyond city limits and even before you depart the mountain metropolis.

Table Mountain

Table Mountain , which at 3000 meters is the highest ridge in the Caucasus, rises above Vladikavkaz as an unmistakable feature of its natural landscape. Table Mountain is depicted on the coat of arms of both the Republic of Ingushetia and Vladikavkaz, for it is located on the border between the two entities. Due in part to the 4th-8th century ruins located on Table Mountain, North Caucasus residents have long viewed it as symbolic of Olympus.

Kosta Khetagurov Park

Kosta Khetagurov Park , the oldest park in the entire North Caucasus, consists of upper and lower terraces along the Terek River, shady pathways which provide welcome relief in the summer heat and a calming lake populated with swans. Cafes, boat rides and other entertainment options combine to create a fun and restful atmosphere .

Vladikavkaz Souvenirs

Like the rest of the Caucasus, the Republic of North Ossetia-Alania offers guests an exquisite array of gifts so you can carry the memory of a Vladikavkaz vacation home with you.

Among the most popular gifts are wine vessels in the shape of a horn, which often include an engraving on a metal border and may be either decorative or unpainted. Dishes, coasters, potholders, fragrant spices and delicious local pies are also popular souvenir choices from Vladikavkaz.

Specialty gifts for men include leather belts, wallets and decorative metal plates, all of which are made with embossed patterns, ornamentation or symbols of the republic such as horfreses, leopards, deer or double-headed eagles.

Women can be presented with openwork earrings, bracelets, pendants, combs and hair clips made of wood, as well as textiles or wool shawls in colorful oriental patterns. Ceramic products suitable for everyday use include coffee cups, small teapots, serving bowls and elegant jugs adorned with national motifs.

National costumes for both genders reflect the vibrancy of the North Caucasian culture of Vladikavkaz and can make an excellent souvenir for relatives and friends.

Attractions

Miscellaneous.