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:
Edexcel questions courtesy of Pearson Education Ltd.
The diagram shows a ray of light incident on a glass block.
a) At which point would you expect the ray to emerge from the block? [2 marks]
b) A ray box is used to produce the ray of light. What hazard is associated with using ray boxes? [1 mark]
c) Explain how you could make a record of the incident ray and the ray inside the block. [3 marks]
a) B. The ray bends toward the normal which rules out C and D . The ray will only travel along the normal if it was to start with, which it was not so it cannot be A .
b) The ray box can get hot and cause burns if touched .
c) Mark with a pencil two or more 'X' on the incident ray .
Then mark on the point where it emerges .
Then lift the block, complete the incident ray and join where it emerges onto the incident ray to produce the refracted ray .
The diagram below 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|
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]
When the angle of incidence reaches 42° the ray begins to reflect instead of refract.
d) Explain what will happen to the ray of light as the angle of incidence is increased from 10° to 80° mentioning angles of reflection and refraction where appropriate. [5 marks]
The light ray changes direction as it enters the glass block . It refracts towards the normal .
b) and c)
Plot both 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.
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 . Instead it begins to reflect off the inside surface  so that the angle of reflection is the same as the angle of incidence .