A boy with a mouth 5cm wide stands 2m away from a plane mirror. Where is his image and how wide is the image of his mouth?

An object of height 4.0cm is placed at a distance of 30cm from the optical centre ‘O’ of a convex lens of focal length 20cm. Draw a ray diagram to find the position and size of the image formed. Mark optical centre ‘O’ and principal focus ‘F’ on the diagram. Also find the approximate ratio of size of the image to the size of the object.

Refractive indices of four media A, B, C and D are given below:

Medium	Refractive index
A B C D	1.33 1.44 1.52 1.65

In which of these four media is the speed of light:

1. Maximum, and
2. Minimum?

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

Show by drawing a ray-diagram that the image of an object formed by a concave lens is virtual, erect and diminished.

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?

If the magnification of a body of size 1m is 2, what is the size of the image?

What are the important differences between looking at a photograph of your face and looking at yourself in a plane mirror?

Draw a ray diagram to show the path of the reflected ray corresponding to an incident ray which is directed parallel to the principal axis of a convex mirror. Mark on it the angle of incident and the angle of reflection.

To find the image distance for varying object distances in case of a convex lens of focal length 15 cm, a student obtains on a screen a sharp image of a bright object by placing it at 20 cm distance from the lens. After that he gradually moves the object away from the lens and each time focuses the image on the screen.

1. In which direction-towards or away from the lens does he move the screen to focus the object?
2. How does the size of image change?
3. Approximately at what distance does he obtain the image of magnification -1?
4. How does the intensity of image change as the object moves farther and farther away from the lens?