Question

what will be the deviation produced when a ray of light is incident on a plane mirror at an angle of incidence 60 degree? 1)30degree 2)90 degree 3)60degree 4)120degree

Answer 1

A ray of light that is incident on to the surface of a plane-mirror is reflected with the angle of incidence equal to the angle of reflection. Suppose that the ray had continued, through the mirror, in a straight line it would make an angle θ with the surface of the mirror. The total angle between the straight-line path and the reflected ray is twice the angle of incidence. This is called the deviation of the light and measures the angle at which the light has strayed from its initial straight-line path.

in this question if angle of incidence is 60° . then angle that incidence ray makes with the mirror surface,ie, THETA =90-60=30°

ANGLE of deviation =2θ=2×30°=60°

see the diagram for reference

Answer 2

Given that,

Angle of incidence of the ray of light is 60 degrees

To find,

The angle of deviation produced.

Solution,

Accoding to the laws of reflection, the angle of incidence is equal to the angle of reflection. It means that the ray will reflect at an angle of 60 degrees.

Angle of deviation,

$\delta =180-(i+r)\\\\\delta =180-120\\\\\delta =60^{\circ}$

So, the angle of deviation is 60 degrees.