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:

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

Draw ray diagrams showing the image formation by a convex mirror when an object is placed:
At infinity.

If an object is placed at a distance of 8cm from a concave mirror of focal length 10cm, discuss the nature of the image formed by drawing the ray diagram.

A doctor has prescribed a corrective lens of power +1.5 D. Find the focal length of the lens. Is the prescribed lens diverging or converging?

How is the reflection of light ray from a plane mirror different from the refraction of light ray as it enters a block of glass?

To construct ray diagram we use two light rays which are so chosen that it is easy to know their directions after reflection from the mirror. List these two rays and state the path of these rays after reflection. Use these rays to locate the image of an object placed between centres of curvature and focus of a concave mirror.

Identify the device used as a spherical mirror or lens in following cases, when the image formed is virtual and erect in each case.Object is placed between infinity and device, image formed is diminished and between focus and optical centre on the same side as that of the object.

List some things that concave lens and convex mirror have in common.

Draw ray diagrams showing the image formation by a concave mirror when an object is placed:Between focus and centre of curvature of the mirror.

“A concave mirror of focal length ‘f’ can form a magnified erect as well as an inverted image of an object placed in front of it.” Justify this statement stating the position of the object with respect to the mirror in each case for obtaining these images.