If a ray of light enters from alcohol to air. The refractive index of alcohol is 1.36. Calculate the speed of light in alcohol with respect to air.

List two possible ways in which a concave mirror can produce a magnified image of an object placed in front of it. State the difference, if any, between these two images.

Name the type of mirrors used in the design of solar furnaces. Explain how high temperature is achieved by this device.

An object of height 2.5 cm is placed at a distance of 15 cm from the optical centre ‘O' of a convex lens of focal length 10 cm. Draw a ray diagram to find the position and size of the image formed. Mark optical centre ‘O', principal focus F and height of the image on the diagram.

Draw ray diagrams showing the image formation by a convex lens when an object is placed:
Between optical centre and focus of the lens.

Draw ray diagrams showing the image formation by a convex lens when an object is placed:
At the focus of the lens.

Draw ray diagrams showing the image formation by a concave lens when an object is placed:Between focus and twice the focal length of the lens.

With the help of a labelled diagram explain how a convex lens converges a beam of parallel light rays.

Refractive indices of four media A, B, C and D are given below:

Medium	Refractive index
A B C D	1.33 1.44 1.52 1.65

In which of these four media is the speed of light:

1. Maximum, and
2. Minimum?

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