# What is wavelength of light a measure of?

1. ### JosephP

4
Is it the wavelength of the electric portion or magnetic portion or something else entirely?

### Staff: Mentor

Welcome to the PF.

If you are asking about EM waves, the wavelengths of the electric field component and the magnetic field component are the same.

http://phys242.ncat.edu/emwave.jpg

3. ### Simon Bridge

15,041
Welcome to PF;
For electromagnetic radiation, i.e. light, the wavelength of the electric field oscillations is the same as for the magnetic field oscillations.

4. ### JosephP

4
I am a undergrad student working on physics degree. I am currently taking an optics class and am trying to get in a better understanding of light. So the wavelength of the electric field oscillations (or mag. field) is the wavelength of the lifgt ie 640nm for red light. This may seam very basic but I want to get this nailed down. Thanks.

5. ### Simon Bridge

15,041
That's right - an EM wave with a wavelength of 640nm would be red light.
Not all red light would have this wavelength though. The ranfe is usually taken to be from 620nm to 750nm.

That would the the wavelength of the magnetic field which is also the wavelength of the electric field - in the EM wave.

As you progress through your studies, you will be introduced to more sophisticated and complete models for how light works. In your undergrad course, you are only laying the foundations. Don't expect too much from it.