NCERT Solutions Curiosity Chapter 10 .3 What Are the Laws of Reflection? — In-text Questions
Book page 15710 Updated on2026-09-05
Q1.
Do you remember doing the activity for observing the reflection of a beam of light from a plane mirror?
Answer
Yes. In Grade 7 a comb was used as a slit-maker: all its openings were covered with black paper except one in the middle, and a torch shone through that single slit to give one thin beam of light travelling along a sheet of white paper. A plane mirror was stood upright on the paper in the path of that beam.
The beam struck the mirror and came away along a new, definite direction — it did not scatter. Tilting the mirror or the torch changed the direction of the beam coming away, but there was always exactly one reflected beam.
Tip: the same set-up is used again in Activity 10.4, this time with the angles actually measured, and in Activity 10.6 with several slits open so that many parallel beams fall on the mirror at once.
Q2.
We have observed images formed by three types of mirrors — plane, concave, and convex. But are there any laws which govern the image formation?
Answer
Yes. Everything a mirror does follows from just two laws of reflection, and they apply to every ray, at every point, on every kind of mirror.
The angle of incidence is equal to the angle of reflection, both measured from the normal at the point of incidence.
The incident ray, the normal at the point of incidence, and the reflected ray all lie in the same plane.
Why two laws are enough: the first law fixes how much the ray is turned; the second fixes the plane in which it is turned. Together they leave only one possible direction for the reflected ray. Once the direction of every reflected ray is decided, the position, size and orientation of the image are decided too — which is why the same two laws explain the same-size image of a plane mirror and the enlarged, inverted image of a concave mirror.