A student investigates the refraction of light through a transparent rectangular block using the pin-trace method. The student draws the outline of the block ABCDABCDABCD on a sheet of paper, draws a normal to side ABABAB, and then draws an incident ray line making an angle of incidence iii with the normal. They place two pins, P1P_1P1 and P2P_2P2, on the incident ray line.
Explain why the pins $P_1$ and $P_2$ should be placed far apart (for example, more than $5.0\text{ cm}$ apart) rather than close together to produce an accurate ray-trace.
Suggest two other practical techniques (concerning the physical alignment or drawing) that the student should use during this experiment to ensure the ray-traced lines are as accurate as possible.
The student plans to investigate the relationship between the angle of incidence $i$ and the angle of refraction $r$ across a wide range. Suggest a suitable range of angles, and list four specific values of $i$ that would be suitable to test this relationship.
100 exam-style questions on CIE IGCSE Physics 3.2.2 Refraction of light. Each one has a worked solution and a mark scheme showing where the marks go.