Images Formed by Sperical Lenses

An image formed by a concave ______ cannot be obtained on a screen.

A diverging mirror of radius of curvature 40 cm forms an image which is half the height of the object. Find the object and image positions.

 Explain why, a stick half immersed in water appears to be bent at the surface. Draw a labelled diagram to illustrate your answer. 

The distance between principal focus and optical centre of the lens is _________.

1. diameter
2. focal length
3. principal axis
4. optical centre

Suppose you have focused on a screen the image of candle flame placed at the farthest end of the laboratory table using a convex lens. If your teacher suggests you to focus the parallel rays of the sun, reaching your laboratory table, on the same screen, what you are expected to do is to move the:

(a) lens slightly towards the screen

(b) lens slightly away from the screen

(c) lens slightly towards the sun

(d) lens and screen both towards the sun

A real image cannot be obtained on a screen.

A concave lens always forms a virtual image.

Define focal length of a divergent lens.