How does a prism affect wavelength?

[caseytrimble]

I know that prisms create dispersion and cause different frequencies of light to travel at different angles relative to the normal, and that the prism affects the wavelength and speed of the waves, but what exactly is the nature of this relationship? Other than spreading various frequencies out, does the wavelength measurably change? If so, how? Does it contract, does it expand?

 

[Born2bwire]

The speed of light changes but the frequency of the light stays the same. So this means that the wavelength must change accordingly since the product of the frequency and wavelength is the speed of light (in this case at least, there is technically a difference between phase and group velocities but no need to get into that here). Since the relationship is directly proportional between the speed of light and wavelength, then the wavelength must decrease since the prism has a higher index of refraction than the air. Of course, if you immersed your prism in some kind of liquid or dielectric that had a higher index of refraction than the prism itself then you should find that the wavelength increases since the speed of light in the prism would be faster than the external background medium.

 

[ProTerran]

Well according to the General Relativity, the electromagnetic disturbance travels at a constant speed called the speed of light. This speed is the same in every medium.

 

[jtbell]

This speed is the same in every medium.

No, it is not. When we say "constant speed of light" we mean in a vacuum.

The speed of light in water was first measured by Fizeau around 1850.

 

[ProTerran]

Ii's true that the speed of light is the maximum speed which electromagnetic disturbance travels in vacuum. But the point is that water is also consisting almost of a vacuum. So in fact what you measure is a delay between absorption and emission of the light passing by given medium (it is stochastic process).

Hope my English is good enough and you get the idea :-)

 

[DaveC426913]

I know that prisms create dispersion and cause different frequencies of light to travel at different angles relative to the normal, and that the prism affects the wavelength and speed of the waves, but what exactly is the nature of this relationship? Other than spreading various frequencies out, does the wavelength measurably change? If so, how? Does it contract, does it expand?

Just to clarify:

What happens in the prism stays in the prism.

When the light emerges, it has the same frequency and wavelength as when it entered. The prism permanently alters nothing but angle.