Physics [2 Mark Question Answer]

Waves A are Gamma radiations.
Waves B are infrared radiations.
In vacuum, both travel with the same speed. Hence, the ratio of their speeds is 1:1.

Two properties of ultraviolet radiation different from the visible light:
1. Ultraviolet radiation can pass through quartz, but they are absorbed by glass.
2. They are usually scattered by the dust particles present in the atmosphere.

(a)

(b) In both the cases the image formed is virtual, upright and on the same side of the lens but the image formed by a convex lens is magnified and that formed by a concave lens is diminished.

Nature of image: Real, inverted and magnified.

(a) A convex lens with short focal length can be used as a magnifying glass.
(b) A simple magnifying glass forma a virtual, erect and magnified image of a tiny object which is distinctly seen by the eye because the eye lens converges the rays to form a real image on the retina.

Ray diagram for the formation of image by a magnifying glass. 

(i) Ultra-violet radiation
(ii) Infra-red radiation

The colour band obtained on a screen on passing white light through a prism is called teh spectrum.

In vacuum both the colours have the same speed.
In glass, red colour has a greater speed.

The completed ray diagram is as shown below :

Frequency of vibration of a stretched string can be increased by:
1. By increasing the tension in the string.
2. By decreasing the length of the string.

Diagram showing divergent action of concave lens:

Diagram showing convergent action of convex lens :

Angle of incidence vs. angle of refraction graph :

Angle of incidence vs. angle of reflection graph :

When a ray of light passes from one medium to another, its direction (except for normal incidence) changes because of change in speed of light. Thus, refraction occurs because light travels with different speed in different media. 

The value of angle of deviation produced by a prism depends upon:
(i) The angle of incidence
(ii) The material of prism
(iii) The angle of prism
(iv) The colour of wavelength of light used.

According to the principle of reversibility, the path of a light ray is reversible.
For e.g. if light travels from air to water along a certain path, then if the path is reversed while travelling from water to air, it will follow exactly the same path.

Angle of íncídence vs angle of deviation graph for a prism

Two advantages of using total reflecting prism as a reflector in place of a plane mirror are:
(i) When total internal reflection occurs, the entire light (100%) is reflected back into the denser medium, whereas in ordinary reflection from plane mirror, some light is refracted or absorbed (i.e. reflection is partial).
(ii) Total reflecting prism gives a much brighter image than that obtained by using the plane mirror.

Factors affecting the critical angle are:
(i) The colour (or wavelength) of light.
(ii) The temperature (on changing the temperature of medium, its refractive index changes).