20 September 2016
A Question which made me wonder why ?
I was revising with my 3 year old son Siddhant …that Moon has no light and it takes light from Sun.
Siddhant promptly asked me, ” Sunlight is yellow and you say Moon reflects Sunlight , then how come Moonlight is white and not yellow ?
Does it make you wonder too ?
Sunlight and Moonlight are actually pure white !
Our Sun is actually white (mixture of all wavelengths of visible spectrum) if we see it from outer space or high-altitude airplanes. Our atmosphere scatters shorter to bigger wavelengths color from sunlight when the white light travels through it.
During day, it scatters violet and blue colors leaving yellowish sunlight (the reason why sky is blue and sunlight is yellow).
During morning and evening, the sun appears reddish because light rays needs to travel longer distance in atmosphere which causes scattering of yellow light too.
The sun emits pretty much equal amounts of the colors of the spectrum, and this is what we normally refer to as white light.
Moon rocks brought to earth actually look a lot blacker than white which proved that Moon is actually made up of dark stuff. The reason the moon looks like it reflects a lot of light is really just that the space outside it reflects none (and thus is very very dark) and that makes the small amount of light reflected by the almost black moon make it look like a pale white.
“White” here just means that there is no color that is really preferentially reflected to make it appear colored.
Eyes are made up of two kinds of light sensitive cells: rods and cones. The cones enable you to see and identify colors, but they need quite a lot of light to work. When the light is less you just see with the rods, which are more sensitive to light, but can’t identify color.
This is why you see the world at night in “black and white.” When we look at Moon, we don’t see colors at all at night, so the moon would pretty much have to be seen as colorless.
Article Credit : Shital Kumar Garg, Scientist, DRDO, Ministry of Defence.