Question

Which prism surface will behave as a mirror?

Answer 1

A mirror is a shiny surface that reflects most of the light falling on it. Observe which surface of the prism will reflect the light falling on it. The surface which reflects light falling on it will act as a mirror. If this reflecting surface is plane then the angle of incidence will be equal to the angle of reflection.

Complete step-by-step answer:
Any shiny surface that reflects that light is called a mirror. The mirror has a transmission coefficient 0 and reflection coefficient 1. As you can see in the figure, that light is normally incident on the surface AC, it gets completely transmitted and no light is reflected from the surface AC, therefore the surface AC of the prism cannot be a mirror. Further light is incident on surface AB of the prism and it gets reflected towards surface BC, therefore, surface AB of the prism acts as a mirror. If you carefully observe the figure, you will notice that the angle of incidence is equal to the angle of reflection. Thus, surface AB of the prism will act as a plane mirror. Again the reflected light from surface AB reaches surface BC of the prism. At the surface BC, the light gets completely transmitted and no light is reflected inside the prism, therefore, surface BC of the prism cannot be a mirror.
Thus, in the given prism only surface AB of the prism acts as a mirror.

Note: A prism is generally made up of glass and it can be used for various purposes. A prism can disperse a polychromatic light (light having multiple wavelengths) falling on it. Both reflection and refraction occur inside the prism. The direction of light can be changed with the help of a prism. To understand the prism it is very important to understand how mirrors can be used to reflect and change the direction of light falling on it.