Light and the spectrum.

[rpapps]

Just like 2 + 2 can approach 5 for extremely large values of 2.

 

[SY]

I'm learning that both wave theory and particle theory are good approximations which tend to be chosen arbitrarily as it suits a purpose. But neither is accurate.

Actually, they're both VERY accurate. You just need to know which is the appropriate one to use for a given situation. If you want to really understand it, you could do no better than the Feynman Lectures, one of the greatest books in the English language.

 

[lndm]

When I said that, I was in the process of reading about it, and copied blindly that I had learned they were inaccurate. In my next post I was having (I think) a revelation. There's more to what I was thinking than I put into words.

I've found some Feynman streaming video. I'll have to install sound in this computer before I watch it, or, does anyone know how to save streaming video to file?

 

[KBK]

I keep staring at the Fenyman book, everytime I walk by it in the bookstore. Good to hear it's worth bothering with.

Right now I'm getting a little existential legwork, with Daniel Pinchbeck's book: 2012: The Return of Quetzalcoatl. Interesting stuff. However, for all it's inherent integrety..Pinchbeck keeps quoting Nietzsche, which when done without discretion or thought...is usually a very bad sign. He seems to be able to keep it straight. A quite erudite book. And informative, internally (bellybutton), at least.

 

[DoctorJ]

 

[KBK]

Although the graph is limited in scope, I don't quite see a brickwall filter aspect associated (in an automatic logical function)with it, re the human eye's sensitivity range.

Nice graph that it is, is there one that show the average eye sensitivity..and the maximum that has been 'scientifically' 'measured' ?(more like dictated to humanity as fact by the act of measurement, which itself can and should be understood as being fully capable of error-and frequently is)

 

[poobah]

you could do no better than the Feynman Lectures

If for no other reason than Feynman is also a damn funny guy. Down to earth and not all "full of himself" as well.

 

[SY]

Well, the great thing about the Feynman Lectures is that he really took trouble to dissect things to the basics (and the basics done HIS way), was very clear on what's postulated versus what's derived, excoriates so-called philosophers of science, and uses basic principles of symmetry at each turn to derive the form of solutions.

It's pretty cool when a text aimed for an introductory undergrad course uses the path integral approach to understand quantum mechanics.

 

[pinkmouse]

I still remember his performance on the NASA board of enquiry for the Space Shuttle disaster. A piece of rubber and a glass of cold water cut right through all the political and engineering gobbledigook that had been prevalent, by both the rest of the commitee and the various witnesses.

 

[lndm]

I have watched the first of a four part lecture (so far) by Feynman at Auckland Uni in 1979. http://www.vega.org.uk/video/subseries/8 . This guy is fascinating and entertaining.

If I understand correctly, Feynman does believe photons are particles, and their existence is arbitrary and independent of other photons.

He describes their behaviour in ways that I believe resemble standing waves. He uses vector analysis to describe quantities of light visible from certain points. Rather than saying this sum represents an amplitude of light, he refers to it as the probability of photons being seen.

In the next video's, Feynman will explain why, I can't wait.

 

[dnsey]

If I understand correctly, Feynman does believe photons are particles, and their existence is arbitrary and independent of other photons.

I'm no more than a layman in such things, but as I understand it, particles are now generally considered to be nothing more (or less) than wave functions anyway.

 

[sinuko]

About the Human’s eye ,this is the “exact” relative spectral response for the photopic vision:
Lambda(nm) Relative spectral response
360 4.00E-06
370 1.20E-05
380 3.90E-05
390 1.20E-04
400 3.96E-04
410 1.21E-03
420 4.00E-03
430 1.16E-02
440 2.30E-02
450 3.80E-02
460 6.00E-02
470 9.10E-02
480 1.39E-01
490 2.08E-01
500 3.23E-01
510 5.03E-01
520 7.10E-01
530 8.62E-01
540 9.54E-01
550 9.94E-01
560 9.95E-01
570 9.52E-01
580 8.70E-01
590 7.57E-01
600 6.31E-01
610 5.03E-01
620 3.81E-01
630 2.65E-01
640 1.75E-01
650 1.07E-01
660 6.10E-02
670 3.20E-02
680 1.70E-02
690 8.21E-03
700 4.10E-03
710 2.09E-03
720 1.05E-03
730 5.20E-04
740 2.49E-04
750 1.20E-04
760 6.00E-05
770 3.00E-05
780 1.50E-05
790 7.00E-06
800 4.00E-06
810 2.00E-06
820 1.00E-06
830 0.00E+00

So 1 W/m2 at 550 is 683 lux and the “same “ 1 w/m2 at 680 nm is 1.1 lux!!!!!

Feynman’s books are wonderful….if you just know the physic.

Sorry for my bad English.
Ciao Paolo

 

[lndm]

I'm no more than a layman in such things,

I'm feeling that way too. Any resemblance to someone who knows, dead or alive, is purely coincidental

About the Human’s eye ,this is the “exact” relative spectral response for the photopic vision

Can I assume this is the visible light equivalent to the Fletcher-Munson curve?

One thing Feynman said that 'caught my ear', was that this theory of what light is and how it reacts, applies to everything. Everything in this universe that is <lol>. I'm hoping his teachings will polish my understanding of acoustics.

 

[sinuko]

"Can I assume this is the visible light equivalent to the Fletcher-Munson curve?"

YES,
but at low light level (<0.1 (or less) lux) the spectral sensitivity change (scotopic vison).
Paolo

 

[dnsey]

I suspect that a large part of the difficulty regarding wave / particle duality is due to the use of outdated models. Clearly, particles and waves were defined - somewhat loosely - long before the advent of modern physics, and those same definitions seem to still be in use for the models (and they are no more than that) used to describe the 'real' (!) universe.

 

[real]

just the stuff in Jackson (shudder!).

I'll second that. Not exactly a 'light' read.

Chris.