Question

What does first law of reflection state?

(a) The incident ray, reflected ray and normal ray, at the point of incidence, are in same plane

(b) The incident ray, reflected ray and normal ray, at the point of incidence, are perpendicular to each other

(c) The incident ray, reflected ray and normal ray at the point of incidence are in different plane

(d) mSin(i)=nSir(r)

I got this question in an international level competition.

This intriguing question comes from Dispersion, Fermat’s Principle & its Application topic in section Optics of Engineering Physics II

Answer 1

The correct answer is (a) The incident ray, reflected ray and normal ray, at the point of incidence, are in same plane

To explain I would say: According to the first law of reflection incident ray, reflected ray and normal ray, at the point of incidence, are in same plane. Whereas mSin(i)=nSin(r) is Snell’s Law where m & n are Refractive index of different medium.