Practical questions
You will complete eight required practical activities if you are studying GCSE Physics and 21 if you are studying GCSE Combined Science. You could be asked questions about the methods, safety precautions you might take, results and conclusions of these experiments.
There are two required practicals in the Light and EM spectrum topic: Investigating refraction in rectangular glass blocks and Investigating how the nature of a surface affects the amount of thermal energy radiated or absorbed.
Edexcel questions courtesy of Pearson Education Ltd.
Sample question 1 - Foundation and Higher
Question
A student investigates how the surface of an object affects the radiation it emits.
The image below shows the equipment he uses:
The cube has four different surfaces. He fills the cube with boiling water so that the temperature of each surface is the same. He uses the radiation sensor to measure the radiation emitted from each surface.
His readings are shown.
a) Draw a line from each surface colour to its correct meter reading.
One has been done for you. [2 marks]
b) The temperature of each surface is the same.
Give a reason why the radiation sensor gives a different reading for each surface. [1 mark]
a)
b) Different surfaces emit radiation at different rates.
Recall that different coloured surfaces emit radiation at different rates. The more radiation which is emitted, the higher the meter reading. Black surfaces are better emitters than silver surfaces and matt surfaces are better emitters than shiny surfaces.
Sample question 2 - Foundation
Question
The diagram shows a ray box shining a ray of light at a semi-circular glass block.
a) Complete the diagram to show the path of the ray of light inside the glass block. [2 marks]
A student shines a ray of light into the block as shown.
He measures the angle of incidence inside the block as shown.
He measures the angle of refraction outside the block as shown.
He repeats these measurements for different angles of incidence.
He records his results in this table and plots a graph.
| Angle of incidence (°) | 10 | 15 | 20 | 25 | 30 | 35 | 40 |
| Angle of reflection (°) | 15 | 23 | 31 | 39 | 49 | 60 | 75 |
| Angle of incidence (°) |
|---|
| 10 |
| 15 |
| 20 |
| 25 |
| 30 |
| 35 |
| 40 |
| Angle of reflection (°) |
|---|
| 15 |
| 23 |
| 31 |
| 39 |
| 49 |
| 60 |
| 75 |
b) Two points are highlighted in the table.
Plot these points on the graph. [2 marks]
c) Draw the curve of best fit. [1 mark]
d) The student continues to increase the angle of incidence until it reaches 80°. The critical angle for this glass is 42°.
Explain what happens to the ray of light as the angle of incidence is increased from 10° to 80°. [6 marks]
a)
The light ray changes direction as it enters the glass block. It refracts towards the normal.
b) and c)
Plot the points and draw a smooth curve of best fit which at least covers all the points.
d) Plan the key points which you should include in your answer. Notice that you are given a hint in the question that something happens at 42°. Explain what happens as the angle of incidence is increased from 10° to 42°. Use data from the graph. Then explain what happens at 42° and for angles above 42°. Use as many key words to describe these effects as you can, such as refraction and total internal reflection.
For example:
As the angle of incidence increases so does the angle of refraction. This means that the graph of angle of refraction against angle of incidence becomes increasingly steep.
At the angle of incidence of 42°, the light stops refracting. This is the critical angle where the light emerges along the boundary. For angles of incidence above 42°, total internal reflection occurs. This is where angle of incidence is equal to the angle of reflection.