List four specific characteristics of the images of the objects formed by convex mirrors.

Which of the following diagrams shows the ray of light refracted correctly?

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.

A boy with a mouth 5cm wide stands 2m away from a plane mirror. Where is his image and how wide is the image of his mouth?

An object is placed at a distance of 15 cm from a concave lens of focal length 30 cm. List four characteristics (nature, position, etc.) of the image formed by the lens.

Draw a diagram to represent a convex mirror. On this diagram mark principal axis, principal focus F and the centre of curvature C if the focal length of convex mirror is 3cm.

What is the position of the image when an object is placed at a distance of 20cm from a concave mirror of focal length 20cm?

An object of height 2.5 cm is placed at a distance of 15 cm from the optical centre ‘O' of a convex lens of focal length 10 cm. Draw a ray diagram to find the position and size of the image formed. Mark optical centre ‘O', principal focus F and height of the image on the diagram.

A convex lens of focal length 25cm and a concave lens of focal length 10cm are placed in close focal contact with each other. Calculate the lens power of this combination.

To find-the image-distance for varying object-distances in case of a convex lens, a student obtains on a screen a sharp image of a bright object placed very far from the lens. After that he gradually moves the object towards the lens and each time focuses its image of the screen.

1. In which direction - towards or away from the lens, does he move the screen to focus the object?
2. What happens to the size of the image - does it increase or decrease?
3. What happen when he moves the object very close to the lens?