Gobil said:but normally the refractive index is described as c/v, where v is the velocity of the light in the medium with index n. so what is traveling faster than c in the case of xrays?
In some states of matter, such as in a vacuum or in certain types of crystals, x-rays can travel faster than light because they have a shorter wavelength and higher frequency than visible light. This allows them to pass through these materials more easily, resulting in a faster speed.
The speed of light in a vacuum is considered to be the fastest possible speed, but this only applies to visible light. X-rays have shorter wavelengths and higher frequencies, which allow them to pass through materials more easily and travel faster than light in certain states of matter.
According to Einstein's theory of relativity, the speed of light in a vacuum is considered to be the fastest possible speed. While x-rays can travel faster than visible light in certain states of matter, they still cannot exceed the speed of light in a vacuum.
X-rays and visible light are both forms of electromagnetic radiation, but they have different wavelengths and frequencies. X-rays have shorter wavelengths and higher frequencies, which give them the ability to penetrate and travel through certain materials more easily, resulting in a faster speed.
Yes, the density and composition of the material can also impact the speed of x-rays. In materials with a higher density or different composition, the x-rays may experience more scattering or absorption, resulting in a slower speed compared to a vacuum or a material with a lower density.