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Re: [Phys-l] refraction question



Forum for Physics Educators <phys-l@carnot.physics.buffalo.edu> writes:
The problem is that there is no mechanism (at least that I can see --
ahem) by which the eye (or a bit of film, or a CCD) will measure the
_wavelength_, rather than the _frequency_. Embed the film (or the CCD) in
plastic or glass, and expose it. It records the same color as it does
"free", in air (I've done this several times).

Seems like pretty good evidence that it is the same color. Which
indicates that color may indeed be a frequency property.

What about an interferometer placed in the water. That too would show no
change in the fringes because both beams would be effected the same. If
only the experimental beam is passed through water and compared to a
reference beam in the air, then you see a change in wave length of the
experimental beam. Is this not evidence that wavelength does indeed
change as the light changes medium?


Your point that Physics should use frequency to describe the color of
light is well taken. I am of the opinion that if you are measuring color
(keep in mind I am teaching at the High School level) you are almost
always doing so in air - in the lab - where it does not make any
difference whether you use frequency or wavelength. Knowing that it is
the frequency that remains constant as the light changes medium and
results in the wavelength and velocity changing is interesting but not
going to help the understanding of color or light or any of their
properties. When they shine their laser pointer into the water tank to
see the path of the light - the path in the water is still red. Opening a
can of (it's really green) worms is not helpful.



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