The following table gives the refractive indices of a few media:

	$1$	$2$	$3$	$4$	$5$
Medium:	Water	Crown glass	Rock salt	Ruby	Diamond
Refractive index:	$1.33$	$1.52$	$1.54$	$1.71$	$2.42$

Use this table to give an example of a medium pair so that light speeds up when it goes from one of these medium to another.

 

The following table gives the refractive indices of a few media:

Use this table to give an example of:

A medium pair so that light slows down when it goes from one of these medium to another.

Refractive indices of four media $A, B, C$ and $D$ are given below:

In which of these four media is the speed of light (i) maximum, and (ii) minimum?

Name the lens which can concentrate sun's rays to a point and burn a hole in a piece of paper.

(Choose from: Convex lens, Concave lens)

Name the point inside a lens through which the light passes undeviated.