experiment to show refraction

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Light Refraction Experiment

March 30, 2020 By Emma Vanstone Leave a Comment

This light refraction experiment might be one of the most simple to set up science experiments we’ve ever tried. It is a bit tricky to explain, but impressive even if you can’t quite get your head around it!

If you like this activity don’t forget to check out out our other easy science experiments for kids .

Materials for Light Refraction Experiment

Paper or card

Instructions

Fill the glass almost to the top.

Draw arrows on one piece of of card or paper. Place the paper behind the glass and watch as the arrow points the other way.

Now try to think of a word that still makes sense if you put it behind the glass.

We tried bud , the green ( badly drawn ) plant is on the opposite side when the paper is not behind the glass.

NOW works well too 🙂

How does this work?

Refraction ( bending of light ) happens when light travels between two mediums. In the refraction experiment above light travels from the arrow through the air, through the glass, the water, the glass again and air again before reaching your eyes.

The light reaching your eye (or in this case our camera) coming from the arrow is refracted through the glass of water. In fact the glass of water acts like a convex lens (like you might have in a magnifying glass). Convex lenses bend light to a focal point . This is the point at which the light from an object crosses.

The light that was at the tip of the arrow is now on the right side and the light on the right side is now on the left as far as your eye is concerned (assuming you are further away from the glass than the focal point.

If you move the arrow image closer to the glass than the focal point it will be the way around you expect it to be!

More Refraction experiments

Create an Alice in Wonderland themed version of this too!

Find out how to make your own magnifying glass .

We’ve also got a fun disappearing coin trick .

Or try our light maze to learn about reflection .

Last Updated on February 22, 2021 by Emma Vanstone

Safety Notice

Science Sparks ( Wild Sparks Enterprises Ltd ) are not liable for the actions of activity of any person who uses the information in this resource or in any of the suggested further resources. Science Sparks assume no liability with regard to injuries or damage to property that may occur as a result of using the information and carrying out the practical activities contained in this resource or in any of the suggested further resources.

These activities are designed to be carried out by children working with a parent, guardian or other appropriate adult. The adult involved is fully responsible for ensuring that the activities are carried out safely.

Cool Light Refraction Science Experiment – Arrow Changes Direction!

Magic trick? No, but the results of this experiment are pretty surprising. Kids (and adults) will stare in amazement and scratch their heads wondering what causes the arrow in this experiment to change direction right before their eyes! The secret is light refraction.

Exploring light refraction couldn’t be easier or more fun, simply preview the experiment with our demonstration video below and find an easy to understand explanation of how it works below.

JUMP TO SECTION:   Instructions  |  Video Tutorial  |  How it Works

Supplies Needed

• Piece of Paper

Light Refraction Science Lab Kit – Only $5

Use our easy Light Refraction Science Lab Kit to grab your students’ attention without the stress of planning!

It’s everything you need to  make science easy for teachers and fun for students  — using inexpensive materials you probably already have in your storage closet!

Light Refraction Science Experiment Instructions

Step 1 – Get a sheet of paper and draw two arrows on it. One arrow near the top and one arrow near the bottom. Make the arrows point in the same direction.

Step 2 – Fill a glass with water.

Step 3 – Slowly lower the piece of paper behind the glass of water.

Step 4 –  Look through the glass of water and watch what happens. Do you know why the arrow appears to change directions? Find out the answer in the how does this experiment work section below.

Video Tutorial

How Does the Science Experiment Work

The scientific concept that is at work in this experiment is called refraction. Refraction is the bending of light. Refraction occurs when light travels from one medium to another (ie. air to water, water to air).

During the experiment, the light traveled from the image through the air, then through the glass cup into the water, and finally out of the glass cup and into the air once more before it reached our eyes. Light refracts as it passes from one medium to the next because it travels at different speeds through those mediums. Light travels fastest through air, a little slower through water, and even slower through glass.

This means that the light bends once when it travels through the glass cup into the water, and then it bends again when it travels out of the glass cup and into the air. As a result, the light paths cross and the image appears to be flipped horizontally (left/right).

Light Refraction Examples

The following are examples of refraction that occur all around us.

• Glasses or Contacts – The lenses of glasses and contacts are designed to bend light in ways that help a persons improve vision.
• Rainbow – Rainbows are formed when the rays of sunlight bend (refract) when they travel through rain drops.
• Cameras – A camera works because the lens causes the light rays to refract. 

More Experiments that Show Light Refraction

Refraction of Light Science Experiment – Watch as the straw appears to bend in this experiment that shows refraction in action.

Ruler Changes Size Science Experiment  – Observe how the size of an object changed when viewed through different liquids. 

I hope you enjoyed the experiment. Here are some printable instructions:

Light Refraction Science Experiment

Instructions.

• Get a sheet of paper, and draw two arrows on it. One arrow near the top and one arrow near the bottom. Make the arrows point in the same direction.
• Fill a glass with water.
• Slowly lower the piece of paper behind the glass of water.
• Look through the glass of water and watch what happens.

Reader Interactions

February 5, 2017 at 9:25 am

THIS IS COOL. MY DAUGHTER WON THE SCHOOL WIDE SCIENCE PROJECT. THANK YOU SO MUCH FOR DOING THIS EXPERIMENT!

April 20, 2018 at 3:07 pm

Cause of the reflection of the water.

September 10, 2019 at 11:45 am

*refraction

January 7, 2021 at 3:53 pm

I can’t get this to work. I have used a round glass and a square plastic container. I’ve moved the piece of paper close to the container of water and father back. I have lowered the paper quickly and very slowly. Clearly it works, so what am I missing? The size of the arrows? The size of the paper?

Help! I teach a science class to elementary school children and would love to do this. Please answer [email protected]

May 23, 2018 at 7:33 am

This is because of refraction

January 22, 2019 at 3:42 am

Wonderful. Thanks for sharing

May 29, 2019 at 8:03 am

It was very useful and unique. It impressed my teacher a lot.

January 7, 2021 at 4:11 pm

I was finally able to get the arrow to change direction, but it appears that the mechanism is not the water, but the shape of the glass. It did not work with a square or wide straight sided glass. It did work in a straight sided narrow glass, but the arrow was distorted and could be manipulated back and forth by moving the paper.

March 2, 2022 at 2:52 am

Wow, this helped me for my school project i won second place thank you so much

August 4, 2022 at 7:27 pm

I tried this in a square glass container and the arrow does not change direction.

Does the concave/convex shape of the glass have something to do with the result?

May 22, 2023 at 10:07 am

That’s a great question. Do you have multiple glass containers to try the experiment with? That way you can test to see if the shape of the contain changes the results of the experiment. If you try it, come back to let us know what you find.

July 31, 2023 at 6:30 pm

It was refraction that caused the change of direction

It is caused by the refraction or the shape of the glass.

September 28, 2023 at 6:22 am

Thnx, I got 3rd position in my competition! 🤤

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Home » Articles » STEM » STEM Science » How to Demonstrate Light Bending or Refraction

How to Demonstrate Light Bending or Refraction

Mirror, mirror on the wall… you wink with your left eye and your mirror image winks with the right. what an annoying copycat well, it’s not his fault – that’s how reflection works. we will learn all about it, but also show something even cooler – refraction.

Reflection and Refraction

Sight is our dominant sense. Most of all information we receive is coming through our vision. That’s huge! But how do we see the world around us? It’s actually not only about our capabilities. Objects must have one important property to be seen: they must reflect light . Light is such a tremendous topic that there is special discipline devoted to studying it – optics . Optics is a part of the physics that studies the light – its properties and the behaviour.

So, let’s talk about two important behaviors of the light: reflection and refraction . Reflection is a familiar concept. You look at any polished surface such as the mirror and you see your own reflection. An image is virtually identical, but it’s reversed in the front-back direction. There are two rays of light in play here, incoming and outgoing . Incoming ray hits the surface under a certain angle and then outgoing ray goes under that same angle in the opposite direction. That’s called Law of reflection .

While passing through more than one medium, the light will be refracted

Refraction , on the other hand, means bending of the light . Bending happens whenever light changes medium in which it’s traveling.

For example, moving from water to air would produce this behavior. That occurs because of the difference in the density of different mediums. Air is in the state of gas and molecules of gas are spread out so there is less chance of light hitting them. But let’s put water into the mix. Here, molecules are more packed and that means light moves slower through them. That speed with which the light moves through a certain medium compared to the speed in a vacuum is called refractive index .

Air, for example, has a refractive index of 1.0003, while water has 1.333. That means light moves much quicker through the air. When light moves from the air into the water it slows down and that makes it change direction.

The science behind the Light bending

In our experiment, a light went from the air through the water and then back through the air to get to the drawing. We explained that light refracts when it changes medium and what does that mean.

In this case, the water behaves like a magnifying glass. Light bends towards the center, narrowing until it gets to the one point which we call focal point . From the focal point, light rays switch direction so the left one goes to the right and the right one goes to the left. The result is that our drawing looks reversed!

Materials needed for the Refraction Demonstration:

You will need a glass of water, some drawings or a pencil and the paper

• Transparent glass or bottle
• Some drawings (or pencil and paper)

Instructions for Light bending:

For step-by-step instructions on how to conduct this experiment watch the video on the beginning of the article or continue reading…

• Draw some images you would like to test
• Pour water into a glass
• Put the image behind the glass and look at it through the water. What do you see?

What will you develop and learn by doing refraction experiment:

• Basics of optics
• What is reflection and Law of reflection
• What is refraction and refractive index
• Scientific method

If you liked this experiment and want more cool stuff to do, we recommend you continue your exploration of physics. We bet you would like to learn how to make a potato battery ! Or try some amazing balloon experiments !

If you’re searching for some great STEM Activities for Kids and Child development tips, you’re in the right place! Check the Categories below to find the right activity for you.

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Refraction of light.

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Refraction is the bending of light (it also happens with sound, water and other waves) as it passes from one transparent substance into another.

This bending by refraction makes it possible for us to have lenses, magnifying glasses, prisms and rainbows. Even our eyes depend upon this bending of light. Without refraction, we wouldn’t be able to focus light onto our retina.

Change of speed causes change of direction

Light refracts whenever it travels at an angle into a substance with a different refractive index (optical density).

This change of direction is caused by a change in speed. For example, when light travels from air into water, it slows down, causing it to continue to travel at a different angle or direction.

How much does light bend?

The amount of bending depends on two things:

• Change in speed – if a substance causes the light to speed up or slow down more, it will refract (bend) more.
• Angle of the incident ray – if the light is entering the substance at a greater angle, the amount of refraction will also be more noticeable. On the other hand, if the light is entering the new substance from straight on (at 90° to the surface), the light will still slow down, but it won’t change direction at all.

Refractive index of some transparent substances

All angles are measured from an imaginary line drawn at 90° to the surface of the two substances This line is drawn as a dotted line and is called the normal.

If light enters any substance with a higher refractive index (such as from air into glass) it slows down. The light bends towards the normal line.

If light travels enters into a substance with a lower refractive index (such as from water into air) it speeds up. The light bends away from the normal line.

A higher refractive index shows that light will slow down and change direction more as it enters the substance.

A lens is simply a curved block of glass or plastic. There are two kinds of lens.

A biconvex lens is thicker at the middle than it is at the edges. This is the kind of lens used for a magnifying glass. Parallel rays of light can be focused in to a focal point. A biconvex lens is called a converging lens.

A biconcave lens curves is thinner at the middle than it is at the edges. Light rays refract outwards (spread apart) as they enter the lens and again as they leave.

Refraction can create a spectrum

Isaac Newton performed a famous experiment using a triangular block of glass called a prism. He used sunlight shining in through his window to create a spectrum of colours on the opposite side of his room.

This experiment showed that white light is actually made of all the colours of the rainbow. These seven colours are remembered by the acronym ROY G BIV – red, orange, yellow, green, blue, indigo and violet.

Newton showed that each of these colours cannot be turned into other colours. He also showed that they can be recombined to make white light again.

The explanation for the colours separating out is that the light is made of waves. Red light has a longer wavelength than violet light. The refractive index for red light in glass is slightly different than for violet light. Violet light slows down even more than red light, so it is refracted at a slightly greater angle.

The refractive index of red light in glass is 1.513. The refractive index of violet light is 1.532. This slight difference is enough for the shorter wavelengths of light to be refracted more.

A rainbow is caused because each colour refracts at slightly different angles as it enters, reflects off the inside and then leaves each tiny drop of rain.

A rainbow is easy to create using a spray bottle and the sunshine. The centre of the circle of the rainbow will always be the shadow of your head on the ground.

The secondary rainbow that can sometimes be seen is caused by each ray of light reflecting twice on the inside of each droplet before it leaves. This second reflection causes the colours on the secondary rainbow to be reversed. Red is at the top for the primary rainbow, but in the secondary rainbow, red is at the bottom.

Activity ideas

Use these activities with your students to explore refration further:

• Investigating refraction and spearfishing – students aim spears at a model of a fish in a container of water. When they move their spears towards the fish, they miss!
• Angle of refraction calculator challenge – students choose two types of transparent substance. They then enter the angle of the incident ray in the spreadsheet calculator, and the angle of the refracted ray is calculated for them.
• Light and sight: true or false? – students participate in an interactive ‘true or false’ activity that highlights common alternative conceptions about light and sight. This activity can be done individually, in pairs or as a whole class .

Useful links

Learn more about different types of rainbows, how they are made and other atmospheric optical phenomena with this MetService blog and Science Kids post .

Learn more about human lenses, optics, photoreceptors and neural pathways that enable vision through this tutorial from Biology Online .

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Simple Science Experiments: Simple Light Refraction Experiment

December 28, 2017 by Selena Robinson 9 Comments

Sharing is caring!

We’re continuing with our simple science experiments this week by taking a look at light refraction. I found a great light refraction experiment video on YouTube and decided to try it with Tigger.

Full disclosure: I didn’t know that refraction was what this experiment demonstrated. I actually had to look it up first. But the experiment is super easy and quick, so that’s a big plus!

Check out this easy way to teach kids about light with this simple light refraction experiment !

And, if you like this one, try some of our other science activities, including how to make an egg float and our easy heat conduction experiment !

Simple Light Refraction Experiment

Watching the original light refraction experiment on YouTube will give you a great look at what’s involved in this activity. But you really only need four things:

• A sticky note (I used a Post-It)
• An empty transparent bottle

Draw two arrows on a sticky note. Make sure that each arrow points in a different direction. Stick the note to a blank wall.

Next, fill up the water bottle. Oh – put the lid on before you do this too! You don’t want water spilling out when you move the bottle around…lol.

The alternating arrows on the note point to the left and the right. Let the kids gradually move the water-filled bottle in front of the sticky note. As the bottle moves in front of the sticky note, something amazing happens.

The arrows appear to change direction! The top arrow, which points to the left, appears to point to the right. And the bottom arrow, which points to the right, appears to point to the left!

Move the bottle back to see the arrows return to their original directions.

So what exactly is going on? We learned that refraction occurs because light bends when it passes through substances, such as water and plastic.

As the light travels through a substance, it becomes concentrated into a focal point, usually near the center. After light passes through the focal point, the rays cross over each other and cause images to appear reversed.

Turns out you can’t believe your eyes after all! 🙂

Books with Simple Science Experiments:

If you liked this simple science experiment, take a look at these books with even more easy activities! (Affiliate links provided here for convenience. For details, see our Disclosure Policy .)

• Science is Simple: Over 250 Activities for Preschoolers
• 365 Simple Science Experiments with Everyday Materials
• The Everything Kids’ Science Experiments Book
• Safe and Simple Electrical Experiments

Don’t miss the rest of our Simple Science Experiments!

For more science homeschooling ideas, follow my It’s Science board on Pinterest!

P.S. Get more fun learning ideas in our email newsletter!

July 13, 2014 at 5:11 pm

I love this demonstration. Must do it again with my kids! Amazing how much you can learn and do with simple household objects!

August 3, 2014 at 1:43 am

Light refraction and how it moves is really so cool. Thanks for linking up to Science Sunday (even when I’m behind on commenting).

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Refraction of Light Experiment

Ever looked at a straw in a cup of water and wonder why it looks bigger and appears to be bent? Or look at something underwater and wondered why it looks so big? These are all a result of the bending of light or refraction. In today’s science experiment on the refraction of light, we’re going to take a closer look at how light bends.

What is refraction?

Refraction is the bending of light. This occurs when light travels through one material to another (ex: air, water, etc…) Unlike objects that reflect, objects that refract light look different. For example, when looking at a glass of water with a straw in it, the straw may appear to be broken. This happens because light moves more slowly in water than in air. As a result, the light bends as it passes from air to water, making the straw appear to be bent.

Materials for light refraction experiment:

• glass jar, container, or vase
• paper (or use the FREE printable Valentine message from down below)
• marker (to write your message if you’re using paper)

Experiment Instructions:

STEP 1: Fill the glass jar almost to the top with water.

STEP 2: If creating your own “secret message” fold the paper in half. Then write your message on one side of the paper. Make sure to write the message backward from right to left. You can create a second message on the back of the folded paper. To make things even easier, you can always download the Free Valentine printable from down below. It’s already done for you!

STEP 3: Next, place the glass jar on a flat surface. Place the folded paper about 3-4 inches behind the jar filled with water.

STEP 4: Looking through the front side of the glass of water, look at your secret message. What do you see?… Your message is not much of a secret anymore!

How does this refraction experiment work?

During the experiment, light travels from the secret message, through the air, through the glass, through the water, then through the glass again, and through the air one more time before finally reaching your eyes.

When light travels through different materials such as the glass jar, air, or water, it travels at different speeds. This causes the light to refract.

Light waves travel faster through the air than they do through water or glass because the air is less dense. It then slows down a little when traveling through the water and is at its slowest, when passing through the glass jar. This is what causes the light to refract or bend and make the secret message change direction. As a result, the message is no longer a “secret” and can be read.

The light that is refracted through the glass of water also acts as a magnifying glass. It makes the image appear larger than it really is. Try moving the image closer to the glass jar and see what happens.

Helpful Resources

If you like kid-friendly science resources and want to learn more about light energy & the other forms of energy, check out my complete energy unit perfect created with kids in mind.

… and if you’d like to use the “secret” messages I used above for the refraction lab, you can download it for free here.

(If you liked these tips, feel free to use this image to save this post to your Pinterest board. )

A third-grade teacher with a passion for creating time-saving classroom resources. She enjoys sharing her attempt to juggle it all... grading papers, lesson planning, student referrals, parent communication, test prep, and so much more all while managing a busy home life with two active teens.

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Refraction of Light Experiment: Easy Science for Kids

By: Author Jacquie Fisher

Posted on Published: February 1, 2019

Categories Kids Activities & Crafts , Science Experiments

Learn about refraction of light with this easy science experiment that can be done at home or in the classroom.

Our easy science experiments are back and this week, we’re adding a touch of ‘magic’!

In my experience, you can AMAZE kids with two types of science activities — the first type are those that show some behind-the-scenes phenomenon like this How Does a Leaf Breathe? experiment!

And the second type are those that seem to work like magic.

Today we’re going to play with that sense of wonder and highlight the science behind light refraction as we bend a pencil without breaking it !

Refraction & Light Experiments: Easy Science for Kids

In the 28 Days of STEM series, this week’s topic is STEM Challenges so we thought we would introduce a science challenge that ‘tricks’ your eyes.

Similar to our Optical Illusion science experiment , light experiments also rely on what our eyes see. 

This quick experiment (actually 2) is so fun to do with kids, takes only 5 minutes and is SUPER EASY — all you’ll need is a pencil and a glass of water. We’re also including affiliate links to some great books and items we used for this experiment.

Since we always pair our experiments with books (it’s a great way to explain & extend the science 😉 here are a few of our favorites on light:

Light is All Around Us – a great introduction to sunlight, shadows and the speed of light.  This is from a great set of early science books which always include a ‘Learn More’ section and easy experiments kids can do after reading the book.  You can see all the books in this series here:  Let’s Read & Find Out Science series for kids !

Explore Light & Optics with 25 Great Projects – includes a number of other cool activities and experiments kids can do with light!  I love the Explore Your World project books — so many awesome themes & topics!

The Bending Pencil Experiment: Light Refraction

Step 1:  Fill a drinking glass or glass jar with water.

We used a mason jar since all of our drinking glasses have an etched design in them.  You’ll get the best results with a clear, glass container for this experiment.

Step 2:  Hold the tip of the pencil while inserting it into the water

You can already see that the pencil appears larger once in the water (as water is also a magnifier — learn more about that in this pine cone experiment ).

Step 3:  Look at the pencil through the side of the glass or jar — did it bend?

You may have to lean the pencil closer to the front of the glass but you should see a distinct ‘break’ in the pencil when you peep through the side of the glass.  As you can see above, the part of the pencil in the water appears to be shifted to the left of where you would expect to see it. 

You can tell kids that this is an optical illusion — your eyes are being ‘tricked’ because the pencil still looks the same when you pull  it out of the water.

Pretty darn cool, huh!?!

Here’s the science behind this cool experiment …

Why Does a Pencil Look Bent in Water?

Refraction is a physics concept that refers to how a wave travels through a medium. 

In this case, we’re looking at how light waves travel through the air, through water and through glass.

Light waves travel faster thought air (which is a less dense material) than they do through water or glass (a more dense material).  So as the light waves enter the glass and water, they slow down and bend into the water. 

Since the light waves are no longer traveling at the same angle, this makes the pencil appear to ‘break’ when you look at it through the glass of water.

How Light Waves Travel through Water

We’re going to try a second cool science experiment:  The Glowing Jar!

We’ll use a jar, some water and a flashlight to get an close-up look at refraction.

Let’s look at light waves without the pencil. 

Since both the glass and the water are more dense materials than air, when you shine a flashlight into the glass (on the left), the light waves will slow down slightly as they enter and then return to normal as they exist the other side so you see one round spot of light.

However, once you add water to the glass (on the right), you can see that the light shining through the glass is more dispursed — now there is BOTH a spot of light and a ‘glowing’ outline of the jar showing on the wall due to how the light waves are refracting (or bending) as they travel through the water.

If you’ve ever been on a boat and looked over the side into the water, this explains why you can see so much below the water — sunlight is refracting (bending) to illuminate a wider area.

One way to explain this to kids is to think about running at the beach and into the water.  When you run on the sand, you can move quickly because you are only running through air. 

However, when you continue to run into the water, you will not be able to move as quickly because water is more dense and slows you down. 

The same applies to beams of light — as they enter water, they slow down and can’t move as quickly.

If you want to see another refraction experiment, visit my friend Erica at What do We do all Day to see how they made an arrow change directions with a glass of water !

If you’d like to explore more with light science and optical illusions, a few fun items along with affiiliates links include:

More Easy Science Experiments!

The Science of Sound: Create Your own Gong

How do Leaves Breathe?

Be sure to join us for the 28 Days of Hands-on STEM Activities hosted by Left Brain, Craft Brain this month! 

Every day, you can find new activities that cover science, technology, engineering and math perfect for kids from preschool thru middle school!

Save Your Favorite Ideas

Refraction of Light Experiment

For an easy and engaging science experiment, try this refraction of light experiment! Kids will be amazed to watch the arrows magically switch directions as they perform this fun science trick.

RELATED: Grow a Rainbow Experiment

Light Refraction Experiment Using Arrows

You will only need a few supplies for this experiment and you probably already have them! In this trick, kids can observe how the water makes their arrows appear as if they are switching directions through light refraction.

You could also play around with different colors, shapes and words to see how they change when water is added into the cups.

Watch the Video Tutorial!

The Science

Here’s what you will observe: As you pour the water into the glass, the arrow will appear like it is magically switching directions.

When light passes through one transparent thing into another (for example: from air through to glass and water) it undergoes what is known as refraction. Refraction happens because light travels at different speeds in different materials (such as air and water). The light bends when it enters the water and then bends again when it leaves the water. This bending of light causes the image to appear flipped in our eyes.

Note: The distance of the arrow to the cup can play a role in whether you see the arrow flip. If the arrow does not flip, you may need to adjust the distance of the arrow to the cup (either closer or further away).

Follow-up experiments: Try doing this experiment again by changing some of the variables. See what happens when you change the image. Or change the colors. You can also experiment with different liquids. Or try filling the glass halfway!

Supplies Needed

• 2 clear glasses
• 2 pieces of white cardstock or paper
• Black marker
• Small bowls or another object to prop the paper on

How to Make the Arrows Reverse

1. Cut out two square pieces of paper.

Using a black marker, draw an arrow on each piece of white cardstock.

2. Prop the pieces of cardstock up against a small bowl or another small object.

Place the arrow about 12 inches back from the glass. If you do not see the arrow flip, you may need to adjust the distance of the arrow to the glass (either closer or further away depending on your position).

3. Arrange the arrows so they are facing opposite directions for two arrows.

You can also do this experiment with just one arrow.

4. Fill the glasses with water.

For an arrow facing left without water, it will flip to face right once the water is added in.

Kids will be amazed to see the arrow flip directions while learning about light refraction!

More Science Experiments

Grow a Rainbow Experiment

How to Make Oobleck

Walking Water Experiment

Lemon Volcano

Related ideas:.

Fluffy Slime Recipe

How to Make Slime With Contact Solution

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Light Refraction Experiments

Refraction of light.

Have you ever noticed if you look through a glass of water , the image behind the glass sometimes looks funny or distorted?

It’s like the glass of water is playing tricks on your eyes.

The trick is actually created by the refraction of light.

Light travels at different speed through different materials.

As a result, the light “turns” when it passes from one medium to another.

There are so many good refraction of light experiments we want to do.

Let’s start with these 2 simples ones.

Light Refraction Experiment

Here are a couple of our favorite optical illusion tricks using the light refraction property.

• a drinking straw or a pen
• clear water or glass of water
• a long clear glass or glass with water
• adult supervision

Instructions

Experiment 1.

• The levels of water in the glass is more than a half of glass.
• Put a straw into the glass with water vertically and watch from the side.

Experiment 2

• Raise the glass or lower your eyes to look at the straw from under the water surface. The straw appears to be bent instead of broken.

Did you try this project?

Follow us on Pinterest and share a photo!

Why: Experiment 1

Light bends when it passes from one medium (air) into another medium of a different density (water). This bending of light, called refraction , causes the straw to look broken ​1​ . The portion of the straw that is submerged in water also appears to be wider than the portion of the straw above the water.

Since the glass is relatively thin, we can assume not much refraction takes place there. So the optical illusions&nbsp ;are mainly caused by the water inside.

However, even though the light bends at the water/air interface, our brain does not know that or account for that. Our brains believe that light always travels in a straight line and extend the light rays backward to a location different from the original straw. That is why the submerged part of the straw appears to be shifted in water.

When I was doing this experiment with my 4 year old daughter, she kept saying that the straw must be broken. But I kept pulling it out of the water to show her that it wasn’t broken at all. She was fascinated.

Why: Experiment 2

Light bends when it passes from water into the air . When the light comes from a location close enough to the surface (or the angle of incidence is larger than water’s critical angle ) the light bends so much that instead of passing out into the air, all of it reflects back into the water as if the water surface were a mirror. This is called  total internal reflection .

Diagram below: When there is total internal reflection, your brain thinks that the underwater fish is at above the water (and upside down).

This is what happened when you looked at the straw from below the water surface. The reflected straw seems to be connecting between the above-water portion and the under-water distortion. That is why the straw looked crooked.

What did you see when you moved your head to different positions? Can you think of some fun experiments to do using this refraction property of light?

• 1. Jiang W, Chen RT, Lu X. Theory of light refraction at the surface of a photonic crystal. Phys Rev B . June 2005. doi: 10.1103/physrevb.71.245115

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