Question

Give reasons :
(a) Red colour is selected for danger signals.
(b) The sky appears dark in space.
(c) The time difference between actual sunset and apparent sunset is
about 2 minutes.
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Answer 1

1. BECAUSE RED IS COLOR WITH LOWEST FREQUENCY RANGE WITHIN VISIBLE LIGHT ELECTRO MAGNETIC SPECTRUM , SO IT SPREADS OUT LEAST AMONG ALL COLORS, IT CAN BE SPOTTED FROM LONGER DISTANCES.THAT CAN PREVENT ACCIDENTS.

2. ACTUALLY, THERE IS NO COLOUR OF UNIVERSE ,AS IT'S MAINLY EMPTY ,AT MOST TIMES THERE IS ABSENCE OF A ENOUGH VISIBLE LIGHT ,SO IT SEEMS DARK ,BUT IF OBSERVE SPACE WITH MICROWAVE FREQUENCY , HYDROGEN ATOMS IN SPACE EMiT INFRARED LIGHT

3. Ans. It is because of atmospheric refraction. When the Sun is slightly below the horizon, the light coming from it travels from less dense to more dense air and is refracted downwards. Thus, the Sun appears to be raised and can be seen 2 min before actual sunrise and 2 min after actual sunset.