Describe the New Cartesian Sign Convention used in optics. Draw a labelled diagram to illustrate this sign convention.

Distinguish between a convex and a concave mirror.

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

Why does a ray falling normally on a plane mirror, retrace its path?

Draw ray diagrams to show the formation of three times magnified (a) real, and (b) virtual image of an object by a converging lens. Mark the positions of O, F and 2F in each diagram.

The magnification of an image formed by a lens is – 1. If the distance of the image from the optical centre of the lens is 35 cm, where is the object placed ? What is the nature and focal length of the lens? If the object is displaced 20 cm towards the optical centre of the lens, where would the image be formed and what will be its nature? Draw a ray diagram to justify your answer.

If the image formed by a lens for all positions of the object placed in front of it is always virtual, erect and diminished, state the type of the lens. Draw a ray diagram in support of your answer. If the numerical value of focal length of such a lens is 20 cm, find its power in new cartesian sign conventions.

An object placed 20cm in front of a mirror is found to have an image 15cm.

1. In front of it,
2. Behind the mirror.

Find the focal length of the mirror and the kind of mirror in each case.

At what distance should an object be placed from a convex lens of focal length 18cm to obtain an image at 24cm from it on the other side? What will be the magnification produced in this case?

The image of a candle flame placed at a distance of 45 cm from aspherical lens is formed on screen placed at a distance of 90 cm from the lens. Identify the type of lens and calculate its focal length If the height of the flames 2cm, find the height of its image.