A student is investigating the refraction of light - Edexcel - GCSE Physics Combined Science - Question 3 - 2021 - Paper 1

By examining the graph in Figure 5, when angle i is 80°, the estimated angle r is approximately 42° ± 2°.

From the graph, it can be observed that as angle i increases, angle r also increases. However, this increase is not in direct proportion, as the increments in angle r become less significant for each equal step in angle i after certain angles.

As light travels from P to Q, the decrease in intensity can be attributed to the refraction of light as it enters the glass block from the air. The absorption of some light by the glass and the change in medium cause the intensity to diminish. Since the frequency remains constant but the wavelength changes, resulting in a loss of energy carried by the light, this contributes to the reduced intensity.

The correct sketch would show the speed of light being lower in the glass than in air. This means that the graph should reflect a slower speed while the light is traveling through the glass block and return to its original speed as it resumes traveling through air.