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 the 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.
If white light passes through prism,we will see a spectrum. What will happen if a red or blue light will fall on a prism
A ray of white light is passed through a glass prism and spectrum is obtained on a screen.
(a) Name the seven colours of the spectrum in order.
(b) Do the colours have the same width in the spectrum ?
(c) Which of the colour of the spectrum of white light deviates (i) the most, (ii) the least ?