State any four characteristics of the image of an object formed by a plane mirror.

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.

A convex lens is immersed in a liquid of refractive index greater than that of glass. How will the nature of lens change?

Draw a ray diagram to show the formation of a virtual magnified image of an object by a convex lens. In your diagram, the position of object and image with respect to the principal focus should be shown clearly.

What do you mean by laterally inverted?

Describe with the help of a ray-diagram, the size, nature and position of the image formed by a convex lens when an object is placed beyond 2f in front of the lens.

List four precautions which a student should observe while determining the focal length of a given convex lens by obtaining image of a distant object on a screen.

The boy walks towards the mirror at a speed of 1m/ s. At what speed does his image approach him?

A communications satellite in orbit sends a parallel beam of signals down to earth. If these signals obey the same laws of reflection as light and are to be focussed onto a small receiving aerial, what should be the best shape of the metal 'dish' used to collect them?

Where must the object be placed for the image formed by a converging lens to be:

1. Real, inverted and smaller than the object?
2. Real, inverted and same size as the object?
3. Real, inverted and larger than the object?
4. Virtual, upright and larger than the object?