The correct arrangement of the following radiations in an increasing order of their wavelengths is :

X-rays, infrared rays, gamma rays, microwaves.

1. gamma rays, infrared rays, X-rays, microwaves
2. gamma rays, X-rays, microwaves, infrared rays
3. gamma rays, X-rays, infrared rays, microwaves
4. X-rays, gamma rays, infrared rays, microwaves

The source of ultraviolet light is —

1. electric bulb
2. red hot iron ball
3. sodium vapour lamp
4. carbon arc-lamp

A radiation P is focused by a proper device on the bulb of a thermometer. Mercury in the thermometer shows a rapid increase. The radiation P is —

1. infrared radiation
2. visible light
3. ultraviolet radiation
4. X-rays

For obtaining the spectrum of infrared radiation, the material of prism should be :

1. glass
2. quartz
3. rock salt
4. does not matter