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.
216 exam-style questions on CIE IGCSE Physics 3.2 Light, covering 3.2.1a Reflection of light, 3.2.1b Images in a plane mirror, 3.2.2 Refraction of light, 3.2.2a Refraction of light, 3.2.2b Total internal reflection, 3.2.2c Refractive index and critical angle, 3.2.2d Optical fibres, 3.2.3a Converging and diverging lenses, 3.2.3b Ray diagrams and the nature of images, 3.2.3c Virtual images and the magnifying glass, 3.2.3d Correcting long-sightedness and short-sightedness, and 3.2.4 Dispersion of light. Each one has a worked solution and a mark scheme showing where the marks go.