A convex lens of focal length 25cm and a concave lens of focal length 10cm are placed in close contact with one another.

1. What is the power of this combination?
2. What is the focal length of this combination?
3. Is this combination converging or diverging?

The radius of curvature of a convex mirror used as a rear view mirror in a moving car is 2.0m. A truck is coming from behind it at a distance of 3.5m. Calculate (a) position, and (b) size, of the image relative to the size of the truck. What will be the nature of the image?

Two lenses have power of

1. +2D
2. –4D

What is the nature and focal length of each lens?

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.

You are provided with two lenses of focal length 20cm and 30cm, respectively. Which lens will you use to obtain more convergent light?

The shiny outer surface of a hollow sphere of aluminium of radius 50cm is to be used as a mirror:

1. What will be the focal length of this mirror?
2. Which type of spherical mirror will it provide?
3. State whether this spherical mirror will diverge or converge light rays.

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.

If the image formed by mirror for all positions of the object placed in front of it is always virtual and diminished, state the type of the mirror. Draw a ray diagram in support of your answer. Where are such mirrors commonly used and why?

The image of an object formed by a mirror is real, inverted and is of magnification - I. If the image is at a distance of 40 cm from themirror, where is the object placed? Where would the image be if the object is moved 20 cm towards the mirror? State reason and also draw ray diagram for the new position of the object to justify your answer.

An object of size 7.0 cm is placed at 27 cm in front of a concave mirror of focal length 18 cm. At what distance from the mirror should a screen be placed, so that a sharp focussed image can be obtained? Find the size and the nature of the image.