The Planck Constant and the Relationship of Frequency to Photon Energy

RE: The Planck Constant and the Relationship of Frequency to Photon Energy

fmilburn — Mon, 14 Sep 2020 17:21:57 GMT

I just reread my blog and realized an error in the statement on the “eye method” for spotting when the LED turns on and what the ability of color blind individuals to detect it. I imagine a color blind person might see something, they just wouldn’t know what color it was. Still, the method is subjective and there will be a difference in the ability of individuals to detect photons at different wavelengths. As well, humans pick up some colors more easily than others and for example can’t see into the IR like some animals. Made a correction in the blog.

RE: The Planck Constant and the Relationship of Frequency to Photon Energy

DAB — Sun, 06 Sep 2020 18:41:33 GMT

Nice experiment.

Did you know that Planck called his constant a fudge factor to get his data to fit his radiation model.?

From my analysis, his radiation law is wrong. Energy does not correspond to the frequency of the photon.

When you use the radiation model it predicts that higher frequency photons have more energy than lower frequency photons.

In the real world, infrared photons do all of the work in thermodynamics. If Planck was right, we would have UV power stations instead of steam power stations.

So there are some major inconsistencies in Quantum Mechanics because of the over use of the Planck constant.

DAB

RE: The Planck Constant and the Relationship of Frequency to Photon Energy

jc2048 — Sun, 06 Sep 2020 10:47:11 GMT

Interesting experiment and good fun.

"... the energy of the emitted photons is only roughly equal to the bandgap energy of the semiconductor material, which gives a much wider spectral linewidth (possibly by a factor of 100) than the injection laser. The linewidth for an LED corresponds to a range of photon energy between 1 and 3.5 KT, where K is Boltzmann's constant and T is the absolute temperature. This gives linewidths of 30 to 40 nm for GaAs-based devices at room temperature."

Optical Fiber Communications. [2nd Ed. Prentice Hall. 1992.]
John M. Senior

His example there is for an infrared LED, of the kind that you'd use to drive glass fibres, but you can rework it for a visible emitter. That suggests that, maybe, you aren't going to get Planck's constant to a high level of accuracy this way.

Curiously, I thought that visible LEDs changed wavelength at low current levels [noticeably: if you're mixing red, green, and blue to give other colours, the eye is very sensitive to even small changes when it comes to judging the resulting colour hues], but perhaps that's not true. I can't point you at a reputable source for that. Everything I ever worked with was PWM, so I can't say from personal experience. Senior is very thorough in his book, but he doesn't mention the effect [other than with the slight change that would come about through the die temperature varying]. One possibility is that what Senior says above is the case at high currents, but maybe the effect diminishes at very low currents in which case the peak might move. Perhaps you might be able to see if that happens with your spectroscope.

RE: The Planck Constant and the Relationship of Frequency to Photon Energy

genebren — Sun, 06 Sep 2020 04:18:46 GMT

Very cool experiments Frank! I had the opportunity to work with and be involved in the development of UV/VIS spectrometers for liquid chromatography systems. The physics, optics and electronics were all very interesting. I salvaged some pretty cool mirrors, lenses, and other cool treasures from the piles of relics we had lying around.

RE: The Planck Constant and the Relationship of Frequency to Photon Energy

jw0752 — Sun, 06 Sep 2020 02:49:44 GMT

Hi Frank,

Wow, what a fun and interesting experiment. I read a great bio on Max Planck a while back. Did you know he was Olivia Newton-John's Grandfather? Also amazing that they were able to get so close to the current value using the instrumentation of their times. These electronic physics experiments are a very welcome addition to the forum.

Thanks for this post

John