In a ray-tracing experiment to locate the image formed by a plane mirror:
A student places two alignment pins, P1 P_1\,P1 and P2P_2P2, along the incident ray path. Suggest why the distance between pins P1 P_1\,P1 and P2 P_2\,P2 should be made as large as possible (e.g., at least 5.0 cm).
The perpendicular distance from the object pin to the reflective surface of the mirror is measured as a=5.4 cma = 5.4\text{ cm}a=5.4 cm. By projecting the reflected rays behind the mirror line, the position of the virtual image is located, and its perpendicular distance to the mirror is measured as b=5.1 cmb = 5.1\text{ cm}b=5.1 cm. State whether these experimental results support the theory that the image distance is equal to the object distance. Justify your statement by referring to the measurements.
Describe one practical source of inaccuracy in this experiment, other than user error, that could explain why a a\,a and b b\,b are not exactly equal.
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.