Q21 of 38 Page 83

Why does a light ray incident on a rectangular glass slab immersed in any medium emerges parallel to itself? Explain using a diagram.

When light rays is incident on the rectangular glass slab immersed in any medium , then it is refracted by the glass slab and after refracting it comes out of the glass and gets another interface of glass and air, so on going from denser to rarer, it bends away from the normal ray. As the glass slab is rectangular in shape and both sides have the same medium. So, the light ray which is incident and the emergent rays are parallel. It can be shown with the help of following diagram:



More from this chapter

All 38 →
19

In which of the following, the image of an object placed at infinity will be highly diminished and point sized?

 20

Identify the device used as a spherical mirror or lens in following cases, when the image formed is virtual and erect in each case.

(a) Object is placed between device and its focus, image formed is enlarged and behind it.


(b) Object is placed between the focus and device, image formed is enlarged and on the same side as that of the object.


(c) Object is placed between infinity and device, image formed is diminished and between focus and optical center on the same side as that of the object.


(d) Object is placed between infinity and device, image formed is diminished and between pole and focus, behind it.

 22

A pencil when dipped in water in a glass tumbler appears to be bent at the interface of air and water. Will the pencil appear to be bent to the same extent, if instead of water we use liquids like, kerosene or turpentine. Support your answer with reason.

 23

How is the refractive index of a medium related to the speed of light? Obtain an expression for refractive index of a medium with respect to another in terms of speed of light in these two media?