Seven original Cambridge-style questions. They target the two places students lose marks on this topic: measuring angles from the surface instead of the normal, and using casual words instead of the exact image-characteristic language.
State the law of reflection.
The angle of incidence is equal to the angle of reflection, both measured from the normal. ✓
"From the normal" is part of the law. Leaving it out can cost the mark.
A ray of light strikes a plane mirror at an angle of 32° to the mirror surface. Calculate the angle of reflection, measured from the normal.
Convert to the normal:
i = 90° − 32° = 58°Law of reflection:
r = i = 58°angle of reflection = 58°
The 32° is to the surface. Always convert first. Writing 32° is the classic error.
State four characteristics of the image formed by an object placed in front of a plane mirror.
Each exact phrase is worth one mark. "Flipped" or "reversed" scores zero. "Same size" without "as the object" is risky.
A student writes that the image in a plane mirror is "reversed and the same size." Explain why this answer would not gain full marks, and give the correct wording.
This topic is marked on precise vocabulary, not loose description. Learn the exact phrases.
A person stands 1.5 m in front of a large plane mirror.
(a) How far behind the mirror does their image appear? [1] (b) What is the total distance between the person and their image? [1](a) The image is as far behind as the object is in front, so 1.5 m behind. ✓
(b) 1.5 m + 1.5 m = 3.0 m ✓
Image distance behind = object distance in front. Total separation is double the object distance.
The diagram shows a ray of light striking a plane mirror. The normal is drawn at the point where the ray hits. The angle between the incident ray and the normal is 50°.
(a) Angle of reflection = 50° (equal to the angle of incidence). ✓
(b) The reflected ray leaves the point on the other side of the normal, at 50° to the normal, travelling up and to the right. ✓✓
The reflected ray is the mirror image of the incident ray across the normal. Draw it with a ruler and an arrow pointing away from the mirror.
The surface of a calm lake acts like a mirror, giving a clear reflection of the trees on the far bank. On a windy day, the same lake gives only a blurred, broken reflection.
Explain, in terms of reflection, why the reflection is clear when the water is calm but blurred when it is rough.
The law of reflection still holds at every tiny point. It is the changing direction of the normal across a rough surface that scatters the light.
Mark this once you have attempted all six and checked your working. It records a Practiced badge on the topic and adds a one-time bonus. Revealing the solutions alone does not count.