How fast a person should drive his car so that the red signal fo light apperas green ?
( Wavelength for red colour = 6200 Å and wavelength for green colour = 5400 Å)

Wavelength of red colour is approximately how many times the wavelength of violet colour ?

Is it possible for a observer to move towards a stationary source emitting red light so that the red light appears to be green for the observer ? Wavelength of green is 5400Ả and that of red is 6200A. Velocity of light is 3 xx 10^(8)" m/s".

Work out the ranges of temperature corresponding to which a star will appear blue and red respectively. Given Wavelength range of blue colour: 4500Å to 5000Å Wavelength range for red colour: 6500Å to 7000Å

Which colour of light has the shorter wavelength-red or violet ?

How the gem stones ruby exhibits red colour and emerald exhibits green colour ?