. Infrared radiations are used for photography in fog


Give reason for the following:

(i) Infrared radiations are used for photography in fog

(ii) Infrared radiations are used for signals during the war.

(iii) The photographic darkrooms are provided with infrared lamps.

(iv) A rock salt prism is used instead of a glass prism to obtain the infrared spectrum.

(v) A quartz prism is required for obtaining the spectrum of the ultraviolet light.

(vi) Ultraviolet bulbs have a quartz envelope instead of glass.

 

Best Answer

(i) Infrared radiations are used for photography in fog because they are not much scattered, so they can penetrate appreciably through it.

(ii) Infrared radiations are used as signals during the war as they are not visible and they are not absorbed much in the medium.

(iii) Infrared lamps are used in dark rooms for developing photographs as they provide some visibility without affecting the photographic film.

(iv) Infrared spectrum can be obtained only by using a rock salt prism because the rock salt prism does not absorb the infrared radiations, whereas a glass prism absorbs them.

(v) A quartz prism is used for obtaining the spectrum of the ultraviolet light as they can pass through quartz whereas ordinary glass absorbs the ultraviolet light.

(vi) Ultraviolet bulbs have a quartz envelope instead of glass as they are not absorbed by quartz whereas ordinary glass absorbs the ultraviolet light.

 

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