uses of wavelength

[bhuvaneshnick]

red light has low frequency and high wavelenth

but the red light become less visibile after travelling .i mean cannot hit the wall which half kilometer from the source.

i need to know what changes in color with high frequency what changes in color with high wavelength

why it cannot hit the wall with same intensity as we seen at source

 

[revrard]

Neither the frequency nor the wavelength of a light wave change during propagation in vacuum or in a uniform medium. A beam of light is in general more or less divergent so that its power is spread over a surface increasing with the distance from the source. Therefore, the power falling onto a surface of given area (and the wave intensity, which is the power falling onto a unit surface) decreases with increasing distance, often as 1/the square of this distance. The beam divergence is far lower in lasers than in normal lamps so that they are far less attenuated. This can be observed with lasers used as pointers or in discotheques.