The power of a combination of two lenses X and Y is 5D. If the focal length of lens X be 15cm:

1. Calculate the focal length of lens Y.
2. State the nature of lens Y.

Which mirror is used as a torch reflector? Draw a labelled diagram to show how a torch reflector can be used to produce a parallel beam of light. Where is the bulb placed in relation to the torch reflector?

Mention the types of mirrors used as,

1. Rear view mirrors.
2. Shaving mirrors.

List two reasons to justify your answers in each case.

An object 5 cm in length is held 25 cm away from a converging lens of focal length 10 cm. Draw the ray diagram and find the position, size and the nature of the image formed.

Name the type of mirror used:

1. By dentists.
2. In solar furnaces. Give two reasons why such mirrors are used in each case.

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

Define 'refractive index of transparent medium'. What is its unit? Which has a higher refractive index, glass or water?

An object 2cm tall is placed on the axis of a convex lens of focal length 5cm at a distance of 10m from the optical centre of the lens. Find the nature, position and size of the image formed. Which case of image formation by convex lenses is illustrated by this example?

A man sits in an optician's chair looking into plane mirror which is 2m away from him and views the image of a chart which faces the mirror and is 50cm behind his head. How far away from his eyes does the chart appear to be?

The radius of curvature of a concave mirror is 50cm. Where should an object be placed in the mirror, so as to form its image at infinity? Justify your answer.