Give the position, size and nature of image formed by a concave lens when the object is placed:

1. Anywhere between optical centre and infinity.
2. At infinit.

A concave lens of focal length 15 cm forms an image 10 cm from the lens. How far is the object placed from the lens? Draw the ray diagram.

1. Draw a diagram to show how a converging lens focusses parallel rays of light?
2. How would you alter the above diagram to show how a converging lens can produce a beam of parallel rays of light.

Draw the ray diagram and also state the position, relative size and nature of the image formed by a concave mirror when the object is placed between its centre of curvature, C and the focus, F.

With the help of a labelled diagram, explain why a tank full of water appears less deep than it actually is.

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.

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.

An object of size 7.0cm is placed at 27cm in front of a concave mirror of focal length 18cm. At what distance from the mirror should a screen be placed so that a sharp focussed image can be obtained? Find the size and nature of image.
[Hint. Find the value of image distance (v) first. The screen should be placed from the mirror at a distance equal to image distance.]

Why does a ray falling normally on a plane mirror, retrace its path?

If the image formed by a lens for all positions of the object placed in front of it is always virtual, erect and diminished, state the type of the lens. Draw a ray diagram in support of your answer. If the numerical value of focal length of such a lens is 20 cm, find its power in new cartesian sign conventions.