State the laws of reflection of light. Describe how you would verify them using a plane mirror strip and pins.

1. 1 · State the two laws. Law 1: the incident ray, reflected ray and normal lie in the same plane. Law 2: ∠i = ∠r.
2. 2 · Set up the mirror. Stand a mirror strip upright along a line M₁M₂ on white paper fixed to a drawing board.
3. 3 · Fix the pins. Fix pins A₁, A₂ on a slanting line. Fix B₁, B₂ in line with the images of A₁ and A₂.
4. 4 · Draw the rays and the normal. [Sketch: mirror line, incident ray A₂O, reflected ray OB₁, normal ON, angles i and r marked]
5. 5 · Measure and record. Measure ∠i and ∠r with a protractor for three different angles. They come out equal.
6. 6 · Conclude. ∠i = ∠r verifies the second law. The rays and the normal lie on the flat sheet, which verifies the first law.

Scoring tip: Always measure both angles from the normal, never from the mirror line. Draw the normal before you measure.