# Dispersion Relation

What is the dispersion relation in photons? "(Frequency momentum or etc)

## Answers and Replies

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Meir Achuz
Science Advisor
Homework Helper
Gold Member
A dispersion relation is the relation between the frequency omega and the wave number k.

Or, said in another way, how the phase speed of light (and hence, the index of refraction) depends on the light's frequency in that specific material/medium.

malawi_glenn
Science Advisor
Homework Helper
lightarrow, why restrict yourself to light? The dispersion relation are for waves, all waves, as far as I have understood it.

lightarrow, why restrict yourself to light? The dispersion relation are for waves, all waves, as far as I have understood it.
Ah, yes, of course, but the OP asked about photons.

malawi_glenn
Science Advisor
Homework Helper
Ah, yes, of course, but the OP asked about photons.
haha yeah now I saw he did! ;-)
Though he asked what dispersion relation was "in general"

Avodyne
Science Advisor
The dispersion relation for photons is
$$\omega=|\vec k|c.$$

Thank you very much everybody. I understood it.