explain the following ;-
a) infrared radiation are used for photography in fog or mist.
b) the photographic darkroom are provided with red lamp.
c) ultraviolet bulb have a quartz envelope instead of glass .
d) infrared radiation are used fo signal during wars.
e) the sky appear blue during daytime.
f) rock salt prism is used instead of glass prism to obtain infrared radiation.
Answers
e) A clear cloudless day-time sky is blue because molecules in the air scatter blue light from the sun more than they scatter red light. When we look towards the sun at sunset, we see red and orange colours because the blue light has been scattered out and away from the line of sight.
a) Infrared radiation are used in photography at night and also in mist and fog because they have long wavelength. As they are having low frequency the energy associated with them is also low so they do not scatter much and can penetrate appreciably through it
b) Darkrooms used red lighting to allow photographers to control light carefully, so that light-sensitive photographic paper would not become overexposed and ruin the pictures during the developing process.
c) that's because uv rays can pass through quartz but not through glass.
