Draw diagram to represent the action of a concave mirror on a beam of parallel light rays. Mark on this diagram principal axis, focus F, centre of curvature C, pole P and focal length ƒ, of the concave mirror.

A student places a candle flame at a distance of about 60 cm from a convex lens of focal length 10 cm and focuses the image of the flame on a screen. After that he gradually moves the flame towards the lens and each time focuses the image on the screen.

1. In which direction-toward or away from the lens, does he move the screen to focus the image?
2. How does the size of the image change?
3. How does the intensity of the image change as the flame moves towards the lens?
4. Approximately for what distance between the flame and the lens, the image formed on the screen is inverted and of the same size?

Find the focal length of a lens of power – 2.0 D. What type of lens is this?

A large concave mirror has a radius of curvature of 1.5m. A person stands 10m in front of the mirror. Where is the person’s image?

What is meant by:
Draw diagram to show the action of convex mirror on a beam of parallel light rays. Mark on this diagram principal axis, focus F, centre of curvature C, pole P and focal length ƒ, of the convex mirror.

At what distance from a converging lens of focal length 12cm must an object be placed in order that an image of magnification 1 will be produced?

Identify the device used as a spherical mirror or lens in following cases, when the image formed is virtual and erect in each case.
Object is placed between device and its focus, image formed is enlarged and behind it.

An object of height 2.5 cm is placed at a distance of 15 cm from the optical centre ‘O' of a convex lens of focal length 10 cm. Draw a ray diagram to find the position and size of the image formed. Mark optical centre ‘O', principal focus F and height of the image on the diagram.