How far should an object be placed from a convex lens of focal length 20 cm to obtain its image at a distance of 30 cm from the lens? What will be the height of the image if the object is 6 cm tall?

An image formed on a screen is three times the size of the object. The object and screen are 80cm apart when the image is sharply focussed.

1. State which type of lens is used.
2. Calculate focal length of the lens.

Which of the following are concave mirrors and which convex mirrors?
Shaving mirrors, Car headlight mirror, Searchlight mirror, Driving mirror, Dentist’s inspection mirror, Torch mirror, Staircase mirror in a double-decker bus, Make-up mirror, Solar furnace mirror, Satellite TV dish, Shop security mirror.

A small object is so placed in front of a convex lens of 5cm focal length that a virtual image is formed at a distance of 25cm. Find the magnification

A student wants to project the image of a candle flame on a screen 90 cm in front of a mirror by keeping the flame at a distance of 15 cm from its pole.

1. Suggest the type of mirror he should use.
2. Determine the linear magnification in this case.
3. Find the distance between the object and its image.
4. Draw ray diagram to show the image formation in this case.

An object placed 45cm from a lens forms an image on a screen place 90cm on the other side of the lens. Identify the type of the lens and find its focal length.

An object is placed at a distance of 10 cm from a convex mirror of focal length 15 cm. Find the position and nature of the image.

With the help of a diagram, explain why the image of an object viewed through a concave lens appears smaller and closer than the object.

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.

State where an object must be placed so that the image formed by a concave mirror is:

1. Erect and virtual.
2. At infinity.
3. The same size as the object.