Question

The angle of incidence for a ray of light passing through the center of curvature of a concave mirror is :
$A{.90^0}$
$B{.180^0}$
$C{.60^0}$
$D{.0^0}$

Answer 1

Hint: From the definition of angle of incidence, it is the angle between the normal and the incident ray. As the light ray passes through the center of curvature it strikes along the normal and retraces. Hence, the angle of incidence is zero.

Complete step-by-step answer

Angle of incidence can be defined as the angle made between the incident ray and the normal of the surface it is striking. According to the laws of reflection, the angle of incidence is equal to the angle of reflection. The light rays travel along a straight line.


When it comes to the spherical surface such as a concave mirror the normal of the surface at that point is along the center of curvature. In other words the light ray or beam passing through the center of curvature is striking the mirror surface along its normal. Due to this the light ray retreats its path making the angle of reflection zero. If the angle of reflection is zero then the angle of incidence also should be zero.

Hence, the correct option is D that is \[{0^o}\] .

Note: When a light ray passes through the focus of the mirror after reflection it moves parallel to the principle axis. Similarly the light ray travelling parallel to the principle axis of the mirror after reflection passes through the focus of the mirror.