Question

When a ray of light propagates from a denser medium to a rarer medium, it bends away from the normal. When the incident angle is increased, the refracted ray deviates more from the normal. For a particular angle of incidence in the denser medium, the refracted ray just grazes the interface of the two surfaces. This angle of incidence is called the critical angle for the pair of media involved.

Answer 1

The angle of incidence at the critical angle is the angle at which the refracted ray grazes the interface, i.e., it refracts along the boundary. At this point, the angle of refraction is \(90^\circ\), so by the law of reflection, the angle of reflection must also be \(90^\circ\). Thus, the correct answer is: \[ \text{(D) } 90^\circ \]