When an object is placed at a distance of 36cm from a convex lens, an image of the same size as the object is formed. What will be the nature of image formed when the object is placed at a distance of:

1. 10cm from the lens?
2. 20cm from the lens?

State one practical application the use of such a lens with the object in position (i) and (ii).

Explain with the help of a diagram, why the concave lens is also called a diverging lens.

With the help of a labelled diagram explain how a convex lens converges a beam of parallel light rays.

A 4 cm tall object is placed on the principal axis of a convex lens. The distance of the object from the optical centre of the lens is 12cm and its sharp image is formed at a distance of 24cm from it on a screen on the other side of the lens. If the object is now moved a little away from the lens, in which way (towards the lens or away from the lens) will he have to move the screen to get a sharp image of the object on it again? How will the magnification of the image be affected?

If the magnification of an image formed by a mirror is positive, what does it mean?

Discuss the case when a convex lens forms a virtual and enlarged image.

It is desired to obtain an erect image of an object, using concave mirror of focal length of 12cm.
Where will the image of this object be, if it is placed 24cm in front of the mirror? Draw ray diagram for this situation also to justify your answer.
Show the positions of pole, principal focus and the centre of curvature in the above ray diagrams.

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

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