Colours

[darkar]

What determines the colour? Frequency or wavelenght?

[marlon]

What determines the colour? Frequency or wavelenght?


Normally high frequencies correspond to small wavelengths, and this correspond to colours that are blue-shifted. In the EM-spectrum blue is high energy, and red is low energy. these colors come from the EM-variant of the Doppler-effect. An EM-spectrum can be "made" when reflected sunlight from a planet undergoed emission or absorption processes when passing through our atmosphere. So we will see lines that move to blue when a planet is moving towards us. lines will be moved to red when the planet moves away from us. This is the EM-Dopplereffect.

[selfAdjoint]

Frequency times wavelength is the speed of light, so they are inversely related and either of them can be used.

[salsero]

Frequency times wavelength is the speed of light, so they are inversely related and either of them can be used.

That's not a complete answer: the wavelength depends also on the medium through which the light passes. The color we see is determined by the frequency.

[Gonzolo]

It depends on the energy of the photons our retina cells receive. This energy would be E = hf or E = hv/\lambda_{eye fluid}, with h plank's constant, and v = c/n_{eye fluid} is the speed of light through the fluid in our eye.

[Doc Al]

Just a note: The energy of a photon depends on its frequency, which does not change when light passes from one medium to another.