Questions regarding light being depicted as a sine wave Light waves are often depicted as sine waves...
Why is it so?
What's actually waving?
And what does the sine wave signify and represent?

What does wavelength of light mean/signify? and how is it calculated for specific colors?
Thank you! :)
 A: Light is an electromagnetic wave. Under certain conditions, Maxwell's equations in a given region admit a solution of the form $\vec{E}=\vec{E}_0\cos(\vec{k}\cdot\vec{x}-\omega t),\,\vec{B}=\vec{B}_0\cos(\vec{k}\cdot\vec{x}-\omega t+\varphi)$.
In the direction of the wavevector $\vec{k}$, this solution propagates with wavenumber $k:=|\vec{k}|$, wavelength $\lambda:=2\pi/k$, frequency $\omega=ck/n$ for refractive index $n$ (in vacuo $n=1$) and phase velocity $v_g:=\omega/k=c/n$.
This isn't the only solution; one can superpose them. An envelope of such waves of various $\omega,\,\vec{k}$ has group velocity $v_p:=\frac{\partial\omega}{\partial k}$ (you can show $v_p=cn=\frac{c^2}{v_g}$).
A: The picture is very missleading. What is waving is an electric field and a magnetic field, therefor we call it an electromagnetic wave. the different colors have different wavelength, which is the distance of two consecutive maxima of the electric field. but the wavelength is so short, one can not really depict it, it is less than $\frac{1}{100000}mm$ but the kind of wave is just the same as the radio waves .
