Question

Explain the phenomenon of total internal reflection with one or two activities.

Answer 1

Total internal reflection is an optical phenomenon that occurs when a ray of light strikes a medium boundary at an angle larger than the critical angle with respect to the normal to the surface. If the refractive index is lower on the other side of the boundary no light can pass through, so effectively all of the light is reflected. The critical angle is the angle of incidence above which the total internal reflection occurs.

Activity:

Place the semi circle glass disc in such a way that its diameter coincides with the interface and its center coincides with center point of the interface.

Now send light from the curved side of the semicircular glass disc. Start with angle of incidence (i) equal to $0^{\circ }$, i.e., along the normal.

Sens laser light along angles of incidences $5^{\circ },{10}^{\circ },{15}^{\circ }$, etc.,

and measure the angle of refraction we will observe that at a certain incident angle the refracted ray does not come out but grazes the interface of incidence separating airand gleen is known as critical anglele.

When the angle of the incidence is grater than critical angle, the light of ray get reflected into denser medium at the interface. This phenomenon is called Internal reflection.