conclusion for refraction experiment

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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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refraction experiment

REFRACTION EXPERIMENT

Aim : To study the phenomenon of refraction of light by using a glass block.

Theory : Light is one of the most fundamental energy forms and an understanding of several of its properties is essential to any understanding of science. In this investigation we would be seeing the different phenomenon of refraction of light.   Refraction is a change in the direction of radiation that occurs when it crosses the interface between two media in which the radiation travels with different speeds. The radiation undergoes a change in speed, in wavelength, and in direction. These are a few common terms in relation to refraction of light:

• Reflection : the process by which radiation that strikes a surface separating two media of different densities is in part or in whole turned back into the medium from which it originated. The radiation rebounds from a barrier in its path without a change in speed.
• Normal line : A line perpendicular to the surface at the point where a ray of light strikes.
• Incident Ray : A ray which impinges upon a surface.
• Refracted Ray : a ray that has changed direction after crossing from one media to another, in which the speed is different.
• Emergent ray : the light ray leaving a medium in contrast to the entering or incident ray.
• Angle of incidence : the angle between the incident ray and a normal.
• Angle of refraction : the angle between the refracted ray and the normal line.
• Index of refraction : the ratio of the speed of light in a vacuum (c) to the speed of light in a different medium (v).

The laws of Refraction are:

• A ray of light that passes through a surface into a denser medium (such as from air to glass) is refracted toward the normal line. A ray that passes through a surface to a less dense medium, (such as from glass to air), is refracted away from the normal line.
• The incident and refracted rays are in the same plane.

This is a preview of the whole essay

• The ratio of the sine of the angle of incidence to the sine of the angle or refraction is a constant, called the relative index of refraction, equal to the ratio of the indices of refraction for the two media. This is known as "Snell's Law".

Where (n) is the relative index of refraction.

• A ray emerging from a parallel sided block is parallel to the ray entering, but is displaced sideways.
• A ray raveling along the normal is not refracted.
• The absolute refractive index  is the ratio compared with the refractive index of a vacuum.  ( n  for a vacuum = 1.000;)
• The relative refractive index  is the ratio of the absolute refractive index of one material compared to that of another, for example from water to glass.

Therefore in this whole experiment we would be calculating the relative refractive index as we are comparing water and glass.

This table shows us the refractive indices of different mediums:

Apparatus :

• Glass block
• White sheet of paper

Fair test :

• Make sure that the glass block is aligned the right way and that it is kept constant so that you get the accurate angles of refraction.
• Make sure that angle of incidence is measured rightly and that the incident ray is drawn in the right manner.
• Make sure that the laser shone correctly over the line drawn for the incident ray, so that you get an accurate refracted ray.
• Make sure that the refracted ray is drawn accurately so that you get an accurate refracted ray. Make sure that the glass block is not displaced so that errors are reduced.
• You should make sure that the laser shone in the right manner over the incident ray drawn.
• Make sure that the reflected ray of the laser is extended so that when measuring the angles there will be lesser anomalies.

DATA COLLECTION:

By looking at Table 1 and 2 we can easily see the angle of incidence, angle of refraction and the angle of emergence. We see that the angle of incidence and the angle of emergence are equal in almost all cases, and if not they are not they are almost equal. The maximum error is of 2 ° in one case, whereas on an average the results have been accurate. There could be many errors which could have resulted in some readings not being right. The glass block could have not been placed the right way. The normal line could have not been drawn accurately or the emergent rays could have been drawn inaccurately. The laser beams are sometimes too thick and therefore this could have resulted in anomaly.

The refractive index of glass before was said to be 1.5 on an average. Taking that into consideration, we can see that the refractive index of glass is proven to be right as they are all almost 1.5. But only 40 ° and 60 ° of angle of incidence have exceeded 1.5 whereas the other degrees are lesser than 1.5 but above 1.4. The average of the refractive indices is 1.49, which tells us that on an average the refractive index of glass was proven right.

CONCLUSION :

Therefore by looking at the table we can conclude and say that the angle of incidence is equal to the angle of emergence. By looking at the drawings we can say that the incident ray is parallel to the emergent ray. Moreover the refractive index of glass is proven to be 1.5 on an average. Finally we can say that the rays lie on the same plane.

Teacher Reviews

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This is a well structured and well written report. 1. The sources of information need to be referenced. 2. The conclusion needs to explain the pattern. 3. The report needs to have an evaluation. ****

Document Details

• Word Count 1022
• Page Count 6
• Subject Science

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GCSE Physics Required Practical: Investigating Reflection and Refraction of Light

• 1.1 Meaning
• 1.2.1 Method
• 1.2.2 Improving Accuracy
• 1.3.1 Method
• 1.3.2 Improving Accuracy

Key Stage 4

Investigate the reflection and refraction of light .

Experiment 1: Reflection from a Plane Mirror

• Place a plane mirror in the centre of a piece of paper and draw a pencil line along its reflective side.
• Use a ray box and a slit to allow a single beam of light to be incident on the surface of the mirror at an angle less than 90°.
• Place a pair of x's on the incident ray and along the reflected ray .
• Remove the ray box and mirror .
• Use a ruler to join the x's with a pair of lines leading to the mirror to show the direction of the incident and reflected rays.
• Use a protractor and ruler to draw a normal line at right angles to the surface of the mirror at the point the light rays meet the mirror .
• Use the protractor to measure the 'i' the angle of incidence and 'r' the angle of reflection .
• Repeat this procedure for a number of different angles of incidence .

Improving Accuracy

Experiment 2: refraction from a rectangular glass block.

• Place a rectangular glass block in the centre of a piece of paper and draw a pencil line around the outside.
• Use a ray box and a slit to allow a single beam of light to be incident on the surface of the glass block at an angle less than 90°.
• Place a pair of x's on the incident ray and along the emergent ray .
• Remove the ray box and glass block.
• Use a ruler to join the x's with a pair of lines leading to the glass block to show the direction of the incident and emergent rays.
• Join the emergent ray and the incident ray with a line to represent the refracted ray .
• Use a protractor and ruler to draw a normal line at right angles to the surface of the glass block at the point the light rays meet the glass block.
• Use the protractor to measure the 'i' the angle of incidence and 'r' the angle of refraction .

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Snell's Law

• Angle of Refraction
• Snell's Law
• Ray Tracing and Problem-Solving
• Determination of n Values

A Lesson from the Laboratory

To begin, consider a hemi-cylindrical dish filled with water. Suppose that a laser beam is directed towards the flat side of the dish at the exact center of the dish. The angle of incidence can be measured at the point of incidence. This ray will refract, bending towards the normal (since the light is passing from a medium in which it travels fast into one in which it travels slow - FST ). Once the light ray enters the water, it travels in a straight line until it reaches the second boundary. At the second boundary, the light ray is approaching along the normal to the curved surface (this stems from the geometry of circles). The ray does not refract upon exiting since the angle of incidence is 0-degrees (recall the If I Were An Archer Fish page). The ray of laser light therefore exits at the same angle as the refracted ray of light made at the first boundary. These two angles can be measured and recorded. The angle of incidence of the laser beam can be changed to 5-degrees and new measurements can be made and recorded. This process can be repeated until a complete data set of accurate values has been collected. The data below show a representative set of data for such an experiment.  

An inspection of the data above reveals that there is no clear linear relationship between the angle of incidence and the angle of refraction. For example, a doubling of the angle of incidence from 40 degrees to 80 degrees does not result in a doubling of the angle of refraction. Thus, a plot of this data would not yield a straight line. If however, the sine of the angle of incidence and the sine of the angle of refraction were plotted, the plot would be a straight line, indicating a linear relationship between the sines of the important angles. If two quantities form a straight line on a graph, then a mathematical relationship can be written in y = m*x + b form. A plot of the sine of the angle of incidence vs. the sine of the angle of refraction is shown below.

The equation relating the angles of incidence (Θ i ) and the angle of refraction (Θ r ) for light passing from air into water is given as

Observe that the constant of proportionality in this equation is 1.33 - the index of refraction value of water . Perhaps it's just a coincidence. But if the semi-cylindrical dish full of water was replaced by a semi-cylindrical disk of Plexiglas, the constant of proportionality would be 1.51 - the index of refraction value of Plexiglas . This is not just a coincidence. The same pattern would result for light traveling from air into any material. Experimentally, it is found that for a ray of light traveling from air into some material, the following equation can be written.

where n material = index of refraction of the material

This study of the refraction of light as it crosses from one material into a second material yields a general relationship between the sines of the angle of incidence and the angle of refraction. This general relationship is expressed by the following equation:

where  Θ i  ("theta i") = angle of incidence

Θ r  ("theta r") = angle of refraction

n i = index of refraction of the incident medium

n r = index of refraction of the refractive medium

This relationship between the angles of incidence and refraction and the indices of refraction of the two media is known as Snell's Law . Snell's law applies to the refraction of light in any situation, regardless of what the two media are.

Using Snell's Law to Predict An Angle Value

As with any equation in physics, the Snell's Law equation is valued for its predictive ability. If any three of the four variables in the equation are known, the fourth variable can be predicted if appropriate problem-solving skills are employed. This is illustrated in the two examples below.

In each of these two example problems, the angle of refraction is the variable to be determined. The indices of refraction (n i and n r ) are given and the angle of incidence can be measured. With three of the four variables known, substitution into Snell's law followed by algebraic manipulation will lead to the answer.

First, use a protractor to measure the angle of incidence. An appropriate measurement would be some angle close to 45-degrees.

Second, list all known values and the unknown value for which you wish to solve:

Third, list the relevant equation:

Fourth, substitute known values into the equation and algebraically manipulate the equation in order to solve for the unknown variable -  Θ r.

0.7071 = 1.33 * sine ( Θ r )

0.532 = sine ( Θ r )

sine -1 (0.532) = sine -1 ( sine Θ r )

32.1 degrees =  Θ r

Proper algebra yields to the answer of 32.1 degrees for the angle of refraction. The diagram showing the refracted ray can be viewed by clicking the View Diagram  button below.

Answer: 34.7 degrees

Measure the angle of incidence - the angle between the normal and incident ray. It is approximately 60 degrees.

List known Values:

n i =1.00 n r =1.52 Theta i = 60 degrees

List Unknown: Find theta r

Substitute into Snell's law equation and perform the necessary algebraic operations to solve:

1.00 • sine(60 degrees) = 1.52 • sine(theta r) 0.8660 = 1.52 • sine(theta r) 0.570 = sine(theta r) 34.7 degrees = theta r

Now draw the refracted ray at an angle of 34.7 degrees from the normal - see diagram below.

Snell's Law provides the quantitative means of answering the question of "By how much does the light ray refract?" The task of answering this question involves using indices of refraction and the angle of incidence values in order to determine the angle of refraction. This problem-solving process is discussed in more detail on the remaining pages of Lesson 2.

Flickr Physics Photo

We would like to suggest ....

• Boundary Behavior Revisited

Turning Arrow (Refraction Experiment)

You will need:

• Draw an arrow pointing left or right on the paper and rest it against something so it is standing up.
• Place a transparent (clear) glass in front of the picture so you can clearly see the arrow through the glass.
• Fill another glass with water and pour it into the first glass.
• Watch your arrow change direction!

The science bit:

• Drawing a different picture and seeing what it looks like when it is refracted!
• Make this refraction experiment even better by trying different liquids – does it look different when using oil, or vinegar (for example)?

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Investigating Reflection ( Cambridge O Level Physics )

Revision note.

Investigating Reflection

Aims of the experiment.

• To investigate reflection by a plane mirror
• Independent variable = angle of incidence, i
• Dependent variable = angle of reflection, r
• Distance of ray box from mirror
• Width of the light beam
• Same frequency / wavelength of the light

Apparatus to investigate reflection

• Set up the apparatus as shown in the diagram
• In the middle of the paper use a ruler to mark a straight line of about 10 cm long
• Use a protractor to draw a 90° line that bisects (cuts in half) the 10 cm line
• Place the mirror on the first line as shown in the diagram above
• Switch on the ray box and aim a beam of light at the point where the two drawn lines cross at an angle
• A point just after leaving the ray box
• The point on the reflected beam about 10 cm away from the mirror
• Remove the ray box and mirror
• Use a ruler to join the two marked positions to the point where the originally drawn lines crossed
• Use the protractor to measure the two angles from the 90° line. The angle for the ray towards the mirror is the angle of incidence, and the other is the angle of reflection
• Repeat the experiment three times with the beam of light aimed at different angles
• An example of the data collection table is shown below:

Example Results Table

Analysis of Results

• The law of reflection states:
• i = angle of incidence in degrees (°)
• r = angle of reflection in degrees (°)
• If the experiment was carried out correctly, the angles should be the same, as shown below:

Correct Results of the Experiment

Law of reflection demonstrated correctly

Evaluating the Experiment

Systematic Errors:

• Use a set square to draw perpendicular lines
• If the mirror is distorted, this could affect the reflection angle, so make sure there are little to no blemishes on it

Random Errors:

• Use a sharpened pencil and mark in the middle of the beam
• Use a protractor with a higher resolution

Safety Considerations

• Run burns under cold running water for at least five minute
• Avoid looking directly at the light
• Stand behind the ray box during the experiment
• Keep all liquids away from the electrical equipment and paper
• Damages on the mirror can affect the outcome of the reflection experiment

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Author: Dan MG

Dan graduated with a First-class Masters degree in Physics at Durham University, specialising in cell membrane biophysics. After being awarded an Institute of Physics Teacher Training Scholarship, Dan taught physics in secondary schools in the North of England before moving to SME. Here, he carries on his passion for writing enjoyable physics questions and helping young people to love physics.