Re: [Phys-l] refraction question

["Pete Lohstreter" <plohstreter@mail.hockaday.org>]

Forum for Physics Educators <phys-l@carnot.physics.buffalo.edu> writes:
> The reason I ask is that suppose you shine red light (say, 680 nm) from
> air into water. Since n = 1.33, both the velocity and wavelength will
> decrease by this factor. Thus, (680 nm)/1.33 = 511 nm. This is the
> wavelength of green light! We've probably all done this demo with a red
> laser, and the beam remains red. So color depends on frequency. In class I
> usually say that color depends on wavelength. Lasers are rated by their
> wavelength. Instead, should lasers -- like tuning forks -- be rated by
> their frequency since this quantity never changes?

But if you were the water - the laser might look green.  Since you are
still in the air where the laser looked red before entering the water and
where you saw it when it left the water (back in the air) , it still
looked red.   When the light enters the water is does slow down.  When it
re-enters the air from the water - it speeds back up and resumes its old
ways - same wavelength - same frequency - same velocity.

I don't see the problem.


Pete Lohstreter                           "Happy is he who gets to know 
The Hockaday School                 the reasons for things. "
11600 Welch Rd                          Virgil (70-19 BCE) Roman poet.
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plohstreter@mail.hockaday.org

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