# Frequency of light?

1. Jan 12, 2008

### dmitrip

Frequency of light???

hello everybody, first of all i would like to thank you in advance for answering my questions:)

I am currently learning about the foundations of Quantum physics and this statement keeps on coming up and I cannot understand it. What is the frequency of light?? I don't understand how light can have a frequency and can you please give me a simple of example of how you can change the frequency of light?

thanks again

2. Jan 12, 2008

### ZapperZ

Staff Emeritus
A rather strange question.

First of all, you should have done classical E&M before this. So haven't you solved for the EM wave using Maxwell equation and got the wave equation? The "frequency" should be rather apparent there. So I'm highly puzzled on why you don't understand how light can have a frequency.

How to change light's frequency? Move the source away or towards you, or you move towards or way from the source (doppler effect). Of have the photon collide with a particle (Compton effect), etc... etc.

I have a feeling, though, that there's some underlying problems with this question.

Zz.

3. Jan 12, 2008

### olgranpappy

at a fixed point in space the electric/magnetic field associated with the light changes in time. The time for the field's amplitude to go from zero up to it's maximum value and back down to zero is half the "period" T. The frequency is one over the period. this is all just like regular waves you probably have studied before.

Different colors of light have different frequencies. etc.

4. Jan 12, 2008

### Mentz114

Light is a wave, waves have frequency and wavelength. The frequency and wavelength correspond physically to the colour we see.

5. Jan 13, 2008