Question

Match the following:

Column 1	Column 2
The centre of a sphere of which a curved mirror is a part.	principle focus
A point midway between the pole and centre of curvature of a curved mirror.	pole
The mid point of a spherical mirror.	centre of curvature
An image of an object which cannot be taken on screen.	diffused reflection
A phenomenon due to which light rays on reflection move in different directions.	virtual image
A phenomenon due to which rays of light change their path on passing through another medium.	mirage
The ratio between the velocity of light in vacuum or air to the velocity of light in some other medium.	periscope
An angle of incidence for which angle of refraction is 90°.	refractive index
A simple device used to see above the heads of crowd.	critical angle
Total internal reflection taking place in hot deserts.	refraction

Answer 1

Column I (The centre of a sphere of which a curved mirror is a part) - Column II (centre of curvature)

1. Centre of curvature is the geometrical centre of the sphere of which the curved mirror is a part.
2. It is denoted by the letter ‘C’.

Column I (A point midway between the pole and center of curvature of a curved mirror) - Column II (principle focus)

1. Principle focus is the point where the light rays after reflection from the curved mirror meet or appear to meet.
2. The distance between the pole and principle focus is called the focal length.
3. focal length is half of the radius of curvature, f =R/2

Column I (The midpoint of a spherical mirror) - Column II (pole)

The point midway of the aperture of the curved part of a spherical mirror is called the pole.

Column I (An image of an object which cannot be taken on screen) - Column II (Virtual image)

1. An image in which can be light rays after reflection appears to meet at the principle focus of the spherical mirror is called virtual.
2. A virtual image can be obtained on the screen.

Column I (A phenomenon due to which light rays on reflection move in different directions) - Column II (diffused reflection).

1. When light rays strike an irregular surface, they are reflected in different directions in an irregular manner.
2. This type of reflection is called diffused reflection.

Column I (A phenomenon due to which rays of light change their path on passing through another medium) - Column II (refraction)

The process of bending of light rays when they enter obliquely from one optical medium to another with different optical densities is called refraction.

Column I (The ratio between the velocity of light in vacuum or air to the velocity of light in some other medium) - Column II (refractive index)

Refractive index is the ratio of speed of light in vacuum to the speed of light in any medium.

Refractive Index = Speed of light in vacuum/ speed of light in medium

R.I. = n₁/n₂

Column I (An angle of incidence for which angle of refraction is 90°) - Column II (critical angle)

A certain angle of incidence for which the angle of refraction becomes 90°.

Column I (A simple device used to see above the heads of the crowd) - Column II (periscope)

1. A periscope is a device for seeing over, around, or through an obstacle that creates a hindrance in direct line-of-sight observation from our eye.
2. It consists of a tube with two mirrors facing each other inclined at an angle of 45° at the bends of the tube.

Column I (Total internal reflection taking place in hot deserts) - Column II (mirage)

1. In desert areas, during noon, the images of distant trees can be observed.
2. Naturally, the images of trees, etc. can be formed only in water.
3. So we can be tricked to believe that the tree seen in the image seems to be situated near some water source.
4. But on reaching the tree, the water source vanishes.
5. This phenomenon is termed mirage.

Hence, the correct match is A-III , B-I , C-II, D-V, E-IV, F-X, G-VIII, H-IX, I-VII, J-VI.