Chemistry question about the speed of light?

Question

Does the speed of light change when we speak about different types of waves; i.e. X-Rays, Gamma Rays, Visible, IR, Microwave? If it does, how does it change?

Answer 1

The speed of light (or electromagnetic radiation of any frequency) IN A VACUUM is a constant. This is what is most commonly called "the speed of light", and symbolized by the letter "c".



However, the speed at which electromagnetic radiation propagates in anything other than a vacuum is less than "c", and it *does* depend on the frequency (or, equivalently, the wavelength) of the radiation. The relationship between the propagation speed and the wavelength is given by something called the dispersion curve or dispersion relation. The ratio of the speed of light in a vacuum to the speed of light in something other than a vacuum (i.e., a material, a plasma) is called the refractive index, and the refractive index of a system depends on the frequency of the radiation. In all cases, though, the refractive index is > 1 (the propagation speed of electromagnetic radiation through a material is always slower than through a vacuum).



A prism would not act to separate the different colors (wavelengths) in white light if the propagation speed of the different wavelengths were the same.



You cannot make a general statement as to how the refractive index changes as a function of wavelength -- it depends on the system through which the radiation is propagating.

Answer 2

All of the specified types are electromagnetic radiation and ALL propagate at the same speed.

Some people seem to be getting confused, the question is not about the medium but the type of radiation.

All electromagnetic radiation travels at the speed of light, the speed of light may vary according to the medium.

Answer 3

All electromagnetic waves travel at the speed of light (3 * 10^8 m/s). Light itself is an electromagnetic wave.



The speed of electromagnetic waves = wavelength * frequency = constant = 3 * 10^8 m/s in vacuum



So the wavelength and frequency may change, but speed stays same through a medium.



All the waves you mentioned X-Ray, IR, UV etc. are all electromagnetic waves having different frequencies. But they are electromagnetic waves, so their speed will be same.

Answer 4

A fundamental observation in physics is that the speed of light is invariant with the reference frames by which it is measured. That is, the speed in a vacuum is C no matter what reference frame or what it's doing. So...no, the speed of light in a vacuum does NOT change with the "types of waves."



But...this is important...the average speed of light through a medium, any medium, other than a vacuum is c < C, slower than the speed of light through a vacuum. And that's where we get the refraction index n = C/c.

Answer 5

X-Rays, Gamma Rays, Visible, IR, Microwave, Radio waves, etc. all travel at the same speed.



When we differentiate between them, we are only talking about a difference in FREQUENCY.



In all cases

frequency * wavelength = speed of light



Note that I said "speed of light" rather than "c".

That is because the speed of light is dependent on the medium.

Answer 6

the speed of light is same in all things

speed of light-3.0 multiplies 10 power 8

Answer 7

This isn't chemistry, it's physics. The speed of ALL of those is the same.

Answer 8

The speed of light is constant and never changes. The wavelength and frequency do, however.

Answer 9

electromagnetic waves have got same velocity