Investigating reflection and refraction of light
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Explainer Video
Summary
Investigating reflection and refraction of light
In a nutshell
By using a ray box and different transparent materials, you will investigate how the reflection and refraction of light changes with differing materials. You will do this by measuring the angle of incidence and measuring the angles of refraction in and out of the different materials.
Equipment list
The following equipment list can be used to conduct the experiment to investigate reflection and refraction in transparent materials.
Equipment | Use |
| Ray box and single slit grating | To create a narrow beam of light. |
| Power supply | To provide power for the ray box. |
| Transparent materials | To reflect and refract the light ray. e.g. glass and Perspex |
| Paper | To show the direction of the light ray. |
| Pencil | To mark the direction of the light ray. |
| Ruler | To ensure the lines of the light ray are drawn straight. |
| Protractor | To measure the angles of the light ray. |
Experimental variables
The independent variable is the variable you change. The dependent variable is the variable that changes depending on the other variables, and is the one you measure. The control variables are the variables that are kept constant.
| Independent Variable | |
| Dependent Variable | |
| Control Variables | |
Safety precautions
When performing experiments, it is very important to consider safety precautions. This is so that no one gets hurt or injured during the experiment.
Hazard | Risk | Safety Measure |
| Ray box | The box gets very hot and could result in a burn. | Do not touch during use or straight after use. Leave it to cool before putting it away. If burnt, run burns under cold water. |
| Light ray | Looking into the light may damage eyes. | Don't look directly at the light. Keep the ray box directed away from you. |
| Dark room | There may be trip hazards that are difficult to see due to the lack of light | Take care when moving about, and try to limit movement. Check for hazards before dimming lights. |
Method
These are the instructions to complete the experiment. Record all measurements taken as you work through the experiment in a table.
 |
|
| 1. | Set up the apparatus as shown in the diagram. The transparent material should be placed on top of the sheet of paper. |
| 2. | Draw pencil lines around the edge of the block. This means it can be placed back if anything goes wrong. |
| 3. | Switch the ray box on and direct the light ray at the side of the block. |
| 4. | Using the protractor, draw a line at to the surface of the glass block, where the light ray hits it. This is the normal. |
| 5. | Position the ray box so that it makes an angle with the normal (angle of incidence). |
| 6. | Mark on the paper:
|
| 7. | Remove the block and, using a ruler, join up these lines to trace the outline of the light ray. |
| 8. | Measure the different angles using a protractor. You should measure three angles, the angle of incidence, the angle of reflection and the angle of refraction (inside the block). |
| 9. | Replace the first transparent material with the second and repeat steps 5-8 (repeat again if using more than two materials). Use the same angle of incidence to make analysis easier. |
Analysis
This is how you will use the data recorded to form conclusions.
| 1. | Compare the angles of incidence, reflection and refraction for each material used. |
| 2. | Compare these to known theory. The angle of incidence and reflection should be the same for all materials, whereas the angle of refraction should be different. |
Conclusion
The results from your experiment should confirm the theory of reflection and refraction. This would mean the angle of incidence and reflection should be the same for all materials used. This is because the law of reflection states than the angle of reflection is equal to the angle of incidence.
However, your results should show that the angle of refraction is different for each material used. This is because of the difference in optical density between each material. Think about which materials have the highest optical density and whether this is shown in your results.
Evaluation
Once you have completed your experiment, it is important to consider how it could be improved. You should come up with ways to improve the accuracy of your values. If you got a result that seems unreasonable, think about why this was.
FAQs - Frequently Asked Questions
How does the angle of refraction change in different materials?
The angle of refraction is different for each material used. This is because of the difference in optical density between each material.
How can a light box be used to investigate refraction?
A light box is used to create a narrow beam of light.
How do you investigate reflection?
By using a ray box and different transparent materials, you can investigate how the reflection and refraction of light by the materials. You can do this by measuring the angle of incidence and measuring the angles of refraction in and out of the different materials.