Background information: Refraction is the bending of light or sound waves. It occurs when the wave moves from one medium to another and a change in speed is forced. Refraction creates optical phenomenon and illusions.
Aim: To investigate how light travels from Perspex to air and air to Perspex and the angles of the bending of light when it travels through different mediums.
Hypothesis: From air to Perspex, the angle of incidence will be bigger than the angle of refraction but from Perspex to air, the angle of incidence will be smaller than the angle of refraction.
- Light source
- Rectangular prism
- Whiter piece of paper
Make sure the AC is not twisted to more than 10 as the light bulb won’t be able to handle it and it might break. This will also cause the AC box to be very hot and thus causing your finger to burn.
Independent variable: Angle of incidence
Dependent variables: Angles of refraction from Perspex to air and air to Perspex.
- The number of slits for every experiment
- The same rectangular prism
- The same light source and
- The same protractor when measuring the angles
- Set up the light source and the slit so that the light shines through the slit creating a thin beam of light on the white paper.
- First, place the rectangular prism on the white piece of paper slightly bend.
- Using the pencil, draw out the shape of the rectangular prism and the line of the light source.
- Next remove the rectangular prism and connect both lines of the light source through the shape of the rectangular prism.
- Using the protractor, draw out the normal through the rectangular prism to show the difference.
- Measure out the angles of incidence and refraction from air to Perspex and Perspex to air.
- Repeat Steps from 2 to 6 except, change the rectangular prism from slightly bend to more bend.
- Repeat Steps from 2 to 6 but change the rectangular prism from slightly bend to most bend.
- Record down the angles in the table and any observations.
Air to Perspex
|Angle of incidence||Angle of refraction|
Perspex to Air
|Angle of incidence||Angle of refraction|
During the three experiments, I observed that the angle of incidence from air to Perspex and the angle of refraction from Perspex to air were similar. The angle of refraction from air to Perspex and the angle of incidence from Perspex to air also close to one another with only a few number difference.
I was able to rely on my experiment results as I recorded my observations more than once and I made sure that the variables were controlled to make sure it was a fair test. The equipments used for the three experiments were the same. The only variables that I changed in the experiments were the angles of the rectangular prism but the prism will have the same material and proportions to get the same effect for every experiment.
The strength of my experiments was that I had my friend to help hold the prism still while I drew the shape of it on the white paper. This was a benefit as it will give the results a better accuracy as we would have to measure the angles based on what we drew out. This also helped me to be able to rely on my experiment results. I could have improved my experiment by repeating the experiments to help me increase the reliability on the results. This will also allow me to compare the results and get the final average out of it instead of just getting one result and relying on it. The method was very useful as it helped me collect relevant data and it proved that my hypothesis was right. My method was good as it was very detailed and clear.
This experiment shows that from air to Perspex, the light ray moved towards the direction of the normal as it was from the less dense material (air) to the more dense material (Perspex). And from Perspex to air, the light ray moved away from the direction of the normal as it was from the more dense material (Perspex) to the less dense material (air). I can also conclude that the angle of incidence from air to Perspex and the angle of refraction from Perspex to air are both almost equal. I can also conclude that my hypothesis is right as from air to Perspex, the angle of incidence will be bigger than the angle of refraction as it moved towards the normal but from Perspex to air, the angle of incidence will be smaller than the angle of refraction as it moved away from the normal.
Sir Issac Newton’s view :
My students did a good job in exploring the experiments that shows refraction of light. This simple experiment explained clearly what happened when it moved from a Perspex to air and back to air to Perspex. I hope they would further investigate many different experiments of light in the future. I am currently further investigating on studying the white light and when it is passed through a prism it forms a spectrum of colours. I want to further deepen my understanding by making the experiment more complex.