The radius of curvature of a spherical mirror is 20 cm. What is its focal length?

You are given kerosene, turpentine and water. In which of these the light travels fastest?

A concave mirror produces three times magnified (enlarged) real image of an object placed at 10 cm in front of it. Where is the image located?

Why do we prefer a convex mirror as a rear-view mirror in vehicles?

A ray of light travelling in air enters obliquely into water. Does the light ray bend towards the normal away from the normal? Why?