N=c/v=λ0/λ (T doesn't change) and v of light is constant

AI Thread Summary
The discussion centers on the relationship between the index of refraction (n), the speed of light (c), and wavelength (λ) in different mediums. It highlights a perceived contradiction in the formula n=c/v, which suggests that the index of refraction is constant for all light in a given medium, while dispersion indicates that n varies with wavelength. Participants clarify that the phase velocity of light in a medium does indeed depend on wavelength, meaning that different wavelengths, such as violet and red light, travel at different speeds in glass. This leads to the conclusion that the index of refraction can vary with wavelength, particularly in the context of dispersion. Overall, the conversation emphasizes the complexity of light behavior in various mediums.
brainyman89
Messages
97
Reaction score
0
n=c/v=λ0/λ (T doesn't change) and v of light is constant in a specific medium(i.e. the ratio is constant in given mediums), so the index of refraction is constant for all light when changing mediums.

If we say that index of refraction differs according to the wavelength, then there is contradiction with the above formula n=c/v that says n is constant in specific medium
 
Science news on Phys.org


what i meant to ask is that the formula n=c/v shows that the index is constant for all light and depends only on the medium. however while explaining the dispersion, they say that the index of refraction depends on the wavelength of every light.

isn't there a contradiction?

thanks for answering
 


The phase velocity of the material, v, is dependent upon the wavelength.
 


Born2bwire said:
The phase velocity of the material, v, is dependent upon the wavelength.

do u mean that the velocity of light in a specific medium is not constant and differs according to the wavelength?

for example do x-rays and radio waves have different speeds in glass?
 


brainyman89 said:
do u mean that the velocity of light in a specific medium is not constant and differs according to the wavelength?

for example do x-rays and radio waves have different speeds in glass?
Yes. You don't even need to go that extreme; violet and red wavelengths have different speeds in glass.

Here is a graph of n vs. λ for several different types of glass: visible wavelengths are shown by the pink band:

dispersion-curve3.png
 
Back
Top