Does light travel at different speeds or one same speed?

Answer 1

Light travels at different speeds in different mediums.

Answer 2

There's more to that question that meets the eye (pun intended).

The answer is that electromagnetic radiation always travels at the same speed, c.

But what about optically dense media? We all know that light appears to slow down as it goes through water. The problem is that the "light" that goes through the medium is actually a mixture of EM radiation (light) and shaking charges in the medium. So this disturbance can travel at less than light speed, so we say that the apparent speed of light in the medium is lower. But the best, truest answer is that actual honest-to-god light always travels at the same speed.

Answer 3

It travels at the same speed in a vacuum no matter how fast or what direction you are traveling when you measure the speed of light.

This is a fundamental postulate Einstein relativity.

In a medium, it gets a lot more complicated especially in a non-linear material, but that is a whole different discussion concerning group, phase, and signal velocities.

Answer 4

All light travels at the same speed throegh a vacuum. Every frequency travels at different speeds through materials. This is what allows for the splitting of light by glass prisms.

Answer 5

When light strikes a material, it interacts with the atoms in the material, and the corresponding effects depend on the frequency of the light and the atomic structure of the material. In transparent materials, the electrons in the material oscillate, or vibrate, while the light is present. This oscillation momentarily takes energy away from the light and then puts it back again. The result is to slow down the light wave without leaving energy behind. Denser materials generally slow the light more than less dense materials, but the effect also depends on the frequency or wavelength of the light. Under certain laboratory conditions, scientists can slow light down. In 2001 scientists brought a beam of light to a halt by temporarily trapping it within an extremely cold cloud of sodium atoms.

Answer 6

What ever gave you that idea? Because it is TRUE!!! Light does indeed travel at measurably different speeds, depending on the medium it is traveling through!
Below is an excellent article on proof of the variance of light speed in different mediums, by Anthony Nannini

Answer 7

Light will travel at different speeds through different mediums. Electromagnetic radiation of different frequencies will travel at different speeds through the same medium,

Answer 8

light travels at different speeds through different mediums.

Answer 9

Lighspeed in vacuum is universaly invariant and exact by definition: 299,792,458 m/sec. The speed of light trhough a medium can be asymptotic to zero.

Google phase and group velocities, and negative refractive index (metamaterials).