In Fig. 3.1, a beam of light enters a transparent block. It makes an angle $\theta$ with the normal as it enters, then passes through the block until it reaches the lower face. The angle between the ray inside the block and the block’s vertical side is $\phi$.
(a(i))[2]
The light moves more slowly in the block than it does in air. Explain how Fig. 3.1 indicates this.
(a(ii))[2]
State what happens to the light’s wavelength and what happens to its frequency as it enters the block.
(b(i))[3]
The transparent material has refractive index $1.6$. The angle $\theta$ is $45^{\circ}$. Determine angle $\phi$.
(b(ii))[2]
At the bottom surface, the angle of incidence $i$ equals $\phi$, and the critical angle for the block’s material in air is $39^{\circ}$. Explain what happens to the light after it reaches the bottom surface.
Worked solution & mark scheme
This 9-mark question has a full step-by-step worked solution and mark scheme. One marking point: “The ray refracts / bends towards the normal” …