In my Kaplan book it says, "Note that as light enters a medium with a different index of refraction, the wavelength changes but the frequency of the light does not".
I google around and everyone seems to repeat the same concepts about the conservation of energy and v = λf, since velocity is less, wavelength increases to maintain constant frequency. The problem is, this just doesn't make sense. The way I understood it back in first year is as follows:
Frequency of light must remain constant as it enters and exits a medium because well.. otherwise they'd "accumulate" behind the slower medium. As light enters a prism, the photons interact with the atoms and are re-emitted, this process takes time. Therefore, although the speed of the photons does NOT change, the macroscopic apparent speed of light does (each photon experiences multiple short "pauses"). In order to ensure constant frequency, light coming in at some angle to the normal bends closer to the normal (shortest distance) as it shortens the distance to be travelled (less velocity + less distance = same time). Since different wavelengths interact differently with atoms due to the natural resonant frequencies, they are slowed down to different extents, so they take different paths in the prism thereby reaching the next interface with different angles of incidence leading to different angles of refraction as per Snell's law (Jesus that was too many differents).
That way, none of light wavelength, frequency or "velocity" really change. The index of refraction changes because the "apparent macroscopic velocity" changes (n = c/v). This causes differences in refraction angles (Snell's law).
My question is, am I right or is Kaplan? or Neither?
Thanks.
I google around and everyone seems to repeat the same concepts about the conservation of energy and v = λf, since velocity is less, wavelength increases to maintain constant frequency. The problem is, this just doesn't make sense. The way I understood it back in first year is as follows:
Frequency of light must remain constant as it enters and exits a medium because well.. otherwise they'd "accumulate" behind the slower medium. As light enters a prism, the photons interact with the atoms and are re-emitted, this process takes time. Therefore, although the speed of the photons does NOT change, the macroscopic apparent speed of light does (each photon experiences multiple short "pauses"). In order to ensure constant frequency, light coming in at some angle to the normal bends closer to the normal (shortest distance) as it shortens the distance to be travelled (less velocity + less distance = same time). Since different wavelengths interact differently with atoms due to the natural resonant frequencies, they are slowed down to different extents, so they take different paths in the prism thereby reaching the next interface with different angles of incidence leading to different angles of refraction as per Snell's law (Jesus that was too many differents).
That way, none of light wavelength, frequency or "velocity" really change. The index of refraction changes because the "apparent macroscopic velocity" changes (n = c/v). This causes differences in refraction angles (Snell's law).
My question is, am I right or is Kaplan? or Neither?
Thanks.
