Question

Do all types of electromagnetic waves propagate with same speed?What is the phase difference between electric field and magnetic field vibrations?Does the direction of electromagnetic wave propagation same as the direction of vibration of electromagnetic waves?

Answer 1

Do all types of electromagnetic waves propagate with same speed?

**Answer:**

In a vacuum electromagnetic waves always propagate with the same speed - speed of light. In other mediums, like air or glass, the speed of propagation is slower. If the speed of light in a vacuum is given the symbol $c_{0}$, and the speed in some a medium is $c$, we can define the index of refraction, $n$ as:

$$n = \frac{c_{0}}{c} > 1.$$

What is the phase difference between electric field and magnetic field vibrations?

**Answer:**

In natural light the phase difference between such components changes continuously and randomly. In completely polarized light this phase difference is strictly constant.

One such case is linear polarization; the phase difference here is 0 or $k\pi$, where $k$ is an integer. The other case is circular polarization, where the phase difference is $\pm \frac{(2k + 1)\pi}{2}$.

Does the direction of electromagnetic wave propagation same as the direction of vibration of electromagnetic waves?

**Answer:**

No, because electromagnetic waves are transverse waves. In a transverse wave, the direction $f$ particle displacement occurs perpendicular to the direction of wave propagation.