Question

AB is a sound wave striking a high wall at an angle of 20°.

The angle between the incident ray and the reflected ray is :

Options

• 70°

• 90°

• 120°

• 140°

Answer 1

140°

Explanation:

The given angle is measured from the wall, so the angle of incidence from the normal is \(90^\circ - 20^\circ = 70^\circ\).

The angle of reflection is also \(70^\circ\), so the angle between the incident and reflected rays is \(70^\circ + 70^\circ = 140^\circ\).