Physics [2 Mark Question Answer]

Infrared spectrum can be obtained only with the help of a rock-salt prism since the rock-salt prism does not absorb infrared radiations whereas a glass prism absorbs them.

(i) For therapeutic purposes.
(ii) In night photography.

When a silver chloride solution is taken in a test tube and is passed from red to violet light no change is seen. But beyond the violet end, the solution first turns violet, and then it turns dark brown.

(i) The wavelength of blue light is nearly 4600 Å.
(ii) The wavelength of red light is nearly 7900 Å.
Both colours have the same speed in a vacuum. Red light has a higher speed in the glass.

The spectrum is the colour band obtained on a screen when white light passes through a prism. The seven prominent colours obtained in the spectrum of white light, in order are Violet, Indigo, Blue, Green, Yellow, Orange, and Red.

(i) In producing vitamin D in plants.
(ii) For sterilizing purposes.

(i) Ultra-violet radiations are of wavelength shorter than that of visible light.
(ii) Ultra-violet radiations are more chemically active than the visible light.

(i) The wavelength of infrared radiations is longer than that of visible light.
(ii) The infrared radiations have more heating effect than that of visible light.

The diagram is shown below:

The complete diagram is given below: