Three convex lenses are available having focal lengths of 4cm, 40cm and 4m respectively. Which one would you choose as a magnifying glass and why?

A convex lens of power 5D and a concave lens of power 7.5D are placed in contact with each other. What is the:

1. Power of this combination of lenses?
2. Focal length of this combination of lenses?

State the two laws of reflection of light.

An object is placed just outside the principal focus of concave mirror. Draw a ray diagram to show how the image is formed, and describe its size, position and nature.

How will you distinguish between a plane mirror, a concave mirror and a convex mirror without touching them?

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

Explain what is meant by a virtual, magnified image.

Why does a beam of light when it enters glass at an angle? Why does it not bend if it inters the glass at right angles?

To construct ray diagram we use two light rays which are so chosen that it is easy to know their directions after reflection from the mirror. List these two rays and state the path of these rays after reflection. Use these rays to locate the image of an object placed between centres of curvature and focus of a concave mirror.

Write the formula for a lens connecting image distance (υ), object distance (u) and the focal length (f). How does the lens formula differ from the mirror formula?