8/17/2019 Does Light Have Timbre?
1/2
5/13/16, 30aves - Does light have timbre? - Physics Stack
Exchange
Page
ttp://physics.stackexchange.com/questions/46631/does-light-have-timbre
sign up log in tour he
_
Physics Stack Exchange is a questionand answer site for active
researchers,academics and students of physics. It's100% free.
Sign up
Here's how it works:
Anybody can ask a question Anybody cananswer
The best answers are votedup and rise to the top
Does light have timbre?
Timbre is a property associated with the shape of a sound wave,
that is, the coefficients of the discrete Fourier transform of the
corresponding
signal. This is why a violin and a piano can each play the same
note at the same frequency yet sound completely different. Now for
light: if you
mix red and blue light, the resulting wave has on average the
same frequency as green, but a different shape. Is this why we
observe it as
magenta instead of green? So can we say light has timbre?
But other colours mixtures don't work! Red+green is yellow, but
yellow is a pure colour, so apparently red+green has no unique
timbre in this
case; the shape of the red+green wave is identical to a
pure yellow wave.
waves visible-light fourier-transform
acoustics
edited Dec 11 '12 at 22:53 asked Dec 11 '12 at 22:48
Ignacio
222 3 5
2
–
BTW, isn't at all true. Your visual apparatus
detects them as the same but they are significantly different in
their finely detailed structure.
"the shape of the red+green wave is identical to a pure yellow
wave"
dmckee !Dec 11 '12 at
22:57
–related: physics.stackexchange.com/questions/48224/…
Chris White Jan 21 '13 at 21:41
2 Answers
Your visual range includes roughly one octave as compared
to roughly twelve in your aural
range. Further your visual system uses only four types of light
sensors each with limited
frequency discrimination, while your hearing has fine frequency
discrimination.
So while light spectra could have harmonic structure your visual
apparatus is ill equipped to
detect it.
answered Dec 11 '12 at 22:56
dmckee !
48.2k 4 70 153
Light is almost always considered to be mathematically described
by a simple clean sine wave.
If you mix red and blue light, "exactly" 2x different in
frequency, unless you do something
clever and special, they'll never be exactly 2x but randomly
shifting in phase over time. It would
be like two flutes playing notes one octave apart, which
might sound sort of like a fundamental
and its lowest harmonic, but that's not what your really wanting
to get at, is it?
But we do something clever and special. There are nonlinear
optical materials. Putting a
pure laser beam through one will result in a modified beam with
a bit of 2x or 3x the frequency.
Put pure red in, get red with a little bit of blue added, and
they're steady in relative phase.
can
Physicists and optics engineers have gotten good at applying
nonlinear optics. Frequency
multipliers allow the making of high quality coherent light in
higher frequencies than can be
made with just lasers.
http://physics.stackexchange.com/users/14454/ignaciohttp://physics.stackexchange.com/questions/tagged/visible-lighthttp://physics.stackexchange.com/questions/tagged/waveshttp://physics.stackexchange.com/questions/tagged/visible-lighthttp://physics.stackexchange.com/questions/tagged/fourier-transformhttp://physics.stackexchange.com/questions/tagged/acousticshttp://physics.stackexchange.com/users/signup?ssrc=hero&returnurl=http%3a%2f%2fphysics.stackexchange.com%2fquestions%2f46631%2fdoes-light-have-timbrehttp://physics.stackexchange.com/users/520/dmckeehttp://physics.stackexchange.com/users/520/dmckeehttp://physics.stackexchange.com/questions/46631/does-light-have-timbre#comment105114_46631http://physics.stackexchange.com/users/10851/chris-whitehttp://physics.stackexchange.com/questions/48224/is-it-possible-that-there-is-a-color-our-human-eye-cant-seehttp://physics.stackexchange.com/questions/46631/does-light-have-timbre#comment96182_46631http://physics.stackexchange.com/users/520/dmckeehttp://physics.stackexchange.com/users/14454/ignaciohttp://physics.stackexchange.com/users/14454/ignaciohttp://physics.stackexchange.com/posts/46631/revisionshttp://physics.stackexchange.com/questions/tagged/acousticshttp://physics.stackexchange.com/questions/tagged/fourier-transformhttp://physics.stackexchange.com/questions/tagged/visible-lighthttp://physics.stackexchange.com/questions/tagged/waveshttp://physics.stackexchange.com/questions/46631/does-light-have-timbrehttp://physics.stackexchange.com/users/signup?ssrc=hero&returnurl=http%3a%2f%2fphysics.stackexchange.com%2fquestions%2f46631%2fdoes-light-have-timbrehttp://physics.stackexchange.com/questions/46631/does-light-have-timbre#http://physics.stackexchange.com/tourhttps://physics.stackexchange.com/users/login?ssrc=head&returnurl=http%3a%2f%2fphysics.stackexchange.com%2fquestions%2f46631%2fdoes-light-have-timbrehttps://physics.stackexchange.com/users/signup?ssrc=head&returnurl=http%3a%2f%2fphysics.stackexchange.com%2fquestions%2f46631%2fdoes-light-have-timbrehttp://physics.stackexchange.com/questions/46631/does-light-have-timbre#http://physics.stackexchange.com/questions/46631/does-light-have-timbre#http://stackexchange.com/
8/17/2019 Does Light Have Timbre?
2/2
5/13/16, 30aves - Does light have timbre? - Physics Stack
Exchange
Page
ttp://physics.stackexchange.com/questions/46631/does-light-have-timbre
At the National Ignition Facility (NIF) at LLNL,
physicists are trying to make hydrogen fusion
practical (or for now, just to get it to happen at all). To get
megajoules of laser light at their
favorite wavelength, the optical system uses big violet crystals
as frequency doublers. Paper
about those crystals: Doublers and Triplers (and
quadruplers) have many more uses in lower energy
experiments.
https://e-reports-ext.llnl.gov/pdf/236677.pdf
Somewhat related to the idea of harmonics - having equally
spaced frequencies with fixed
phase relations - is light (usually infrared or THz range) made
in frequency combs. The spacing
is less than the fundamental frequency, and may be quite small.
See
for an explanation with colorful illustrations.
http://www.laserfocusworld.com/articles/print/volume-48/issue-01/features/frequency-
combs-make-their-way-to-the-masses.html
answered Dec 14 '12 at 6:35
DarenW
4,198 1 16 30
http://physics.stackexchange.com/users/353/darenwhttp://physics.stackexchange.com/users/353/darenwhttp://www.laserfocusworld.com/articles/print/volume-48/issue-01/features/frequency-combs-make-their-way-to-the-masses.htmlhttps://e-reports-ext.llnl.gov/pdf/236677.pdf
