Paper 2 · refraction; critical angle; total internal reflection
Fig. 7.1 shows a ray AB in one medium striking boundary PQ at 55° to the normal and refracting into ray BC in the other medium at 35° to the normal. Using the figure, state whether the glass lies above or below the line PQ.
Model answer
below
Also accepted: below PQ, below the line PQ
Explanation: The stronger bending of the ray towards the normal (55° down to 35°) on crossing into the lower medium shows light is slowing down there, consistent with the glass, the optically denser medium, lying below line PQ.
Derived from ZIMSEC Physics Paper 2, November 2004, Q7