This thread got me to thinking, and then to doing some digging!

I wanted to find-out how much Rayleigh scattering varies by wavelength, so that we could adjust qumefox's #'s to account for the change in actual beam intensity based on a laser's wavelength.

Turns out a fella by the name of Lord Rayleigh (hence the name, and also why the first word should be capitalized

) figured this out way back in the 1800's!

He determined that this amount varies inversely proportional to the wavelength of the light raised to the 4th power.

So we can now calculate the difference in Rayleigh scattering between a 532nm green laser and other wavelengths, in order to determine how much we need to adjust the apparent beam intensity to correct this difference!

So based on that, here is the "approximate"

difference in Rayleigh scattering between a 532nm green laser and other common laser wavelengths -

635nm - 0.49266490683388707592096813556886

650nm - 0.44873826309162844438219950281853

660nm - 0.42215388175097666707984764583813

445nm - 2.0427089195236108955687445081855

405nm - 2.9773263176444960813623876252967

But that's not the end of the story! One of the articles I came across indicated that modern references to Rayleigh scattering often forget to include an

**additional** factor - one that

**also** varies by wavelength!

Atmospheric Extinction
Well, it turns-out that the refractivity of air

**also** varies with wavelength! -

Dispersion
Now normally, when a web page claims other references are wrong, I take it with a grain of salt. But this is coming from an

**extremely** authoritative source. These folks' careers depend on making

**EXTREMELY** accurate calculations regarding such things.

So, unlike crazy Google ATM

, I'm going to assume they are a more accurate reference than Wikipedia!

According to this reference, accounting for this extra factor, the change in Rayleigh scattering actually varies by the inverse of the wavelength raised to approximately the 4.08th power across the visible spectrum.

Using these revised calculations, the approximate difference in Rayleigh scattering between a 532nm green laser and other common laser wavelengths is now -

635nm - 0.48573864900825677601320307593276

650nm - 0.44160396556074654015153702131358

660nm - 0.41493512744940499532617990819131

445nm - 2.0720995430911201003047269051986

405nm - 3.043007095689047987747722875912

So, assuming the quoted Chroma values were correct, the revised beam intensity values (including Rayleigh scattering wavelength adjustments), would be approximately -

200mw 635nm red = 23.827mw green

200mw 650nm red = 10.680mw green

And for the other examples given -

1W 445nm = 99.270mw green

600mw 405nm = 9.6077mw green

qumefox, given that the commonly-used LPC LOC is typically spec'd at

**660nm,** I am curious what equivalent 532 green mw your program gives you for that wavelength?