Sure, that seems reasonable – although I’ve not seen anything on this.

The two graphs are pretty standard. The rainbow will always be a medium loop and a sqiggle, the prism a horse shoe shape.

Clearly they are both dispersive

Well, the rainbow differs in having interference effects – I don’t think there’s any “need” for dispersion at all (I think I ran a simulation with constant refractive index and it was very similar, it was over a year ago now). I have some code, will run it – takes a while though due to the numerical instability of the all known Mie scattering solutions.

You’re being very coy about explaining something soon and not mentioning what the bigger problem is so I can get a handle on what you mean!

Yes, I am, I will make a post pretty soon though

Right, yes, that is not white light separation that is blackbody then subtracting atmospheric absorption and adding in all the other effects we just mentioned dispersion.

“Also, the difference between different rainbows or different white light dispersions is far smaller than between the two classes.”

Sure, that seems reasonable – although I’ve not seen anything on this.

“Superficially thats my problem, but it’s just an example of a much bigger problem. One which I will explain soon I reckon. The interesting thing though, is that every scientist I have spoken to about it thought they were qualitatively the same, which they certainly are not. The amount of prisms I seen dawn with a pink is quite remarkable too.”

So that doesn’t explain to me what you are trying to say Clearly they are both dispersive – so what is your beef? that they are different types of dispersion and that the conflation of the two is a mistake? Or are you more annoyed about the adding of colours in a prism spectrum to make it match up with rainbows we see in the sky? You’re being very coy about explaining something soon and not mentioning what the bigger problem is so I can get a handle on what you mean!

So am I correct in thinking the problem you have here is semantics?

Not at all

and

Does that mean to say that you reserve ‘rainbow’ to mean a continuos spectrum of colours with continuos-equivalent spectral densities at each wavelength? probably not?

Hell no!

because there’s no standard for a rainbow though right, it depends on the water droplet size mixture (there will be some sort of mental distribution, I think it’s a power law without looking), the finite diameter of the sun, aerosol content, the time of day etc. etc.

indeed, it’s fucked: http://www.philiplaven.com/p2.html

Eventually, every rainbow is different – so the only definition I can arrive at is that it’s a separation of white light into some arrangement of colours.

How about – “those colourful things that you sometimes see opposite the sun after it rains?”
Also, the difference between different rainbows or different white light dispersions is far smaller than between the two classes.

So the problem you have is the conflation of public awareness of a ‘rainbow’ from a prism and a ‘rainbow’ from a rainbow being identical? As in sound of music stuff being identical to rainbows and prisms in real life? I think as long as it helps people understand that it essentially comes from the similar dispersive mechanisms this is an example of simplification for understanding, the complexity can be added in just a couple of minutes explanation later.

Superficially thats my problem, but it’s just an example of a much bigger problem. One which I will explain soon I reckon. The interesting thing though, is that every scientist I have spoken to about it thought they were qualitatively the same, which they certainly are not. The amount of prisms I seen dawn with a pink is quite remarkable too.

Just a couple of other things that you’re probably aware of:

The bulb used in the picture from wikipedia has a very different spectrum to the spectrum of the sun so the spectral content will be different and

Sure, it’s one of the reasons why I did calculations instead of using the images. That and the problem of the difference between cameras spectral sensitivity and our eyes spectral sensitivity – and the obvious photoshopping.

the rainbow in real life is occurring on a background of Raleigh scattering – spectral densities at those blue wavelengths for the rainbow are reduced through scattering so appearances are going to be deceiving.

The choice of colour space goes a long way to reducing this – but not all the way I admit.

So am I correct in thinking the problem you have here is semantics? and

Does that mean to say that you reserve ‘rainbow’ to mean a continuos spectrum of colours with continuos-equivalent spectral densities at each wavelength? probably not?

because there’s no standard for a rainbow though right, it depends on the water droplet size mixture (there will be some sort of mental distribution, I think it’s a power law without looking), the finite diameter of the sun, aerosol content, the time of day etc. etc.

Eventually, every rainbow is different – so the only definition I can arrive at is that it’s a separation of white light into some arrangement of colours.

So the problem you have is the conflation of public awareness of a ‘rainbow’ from a prism and a ‘rainbow’ from a rainbow being identical? As in sound of music stuff being identical to rainbows and prisms in real life? I think as long as it helps people understand that it essentially comes from the similar dispersive mechanisms this is an example of simplification for understanding, the complexity can be added in just a couple of minutes explanation later.

Just a couple of other things that you’re probably aware of:

The bulb used in the picture from wikipedia has a very different spectrum to the spectrum of the sun so the spectral content will be different and

the rainbow in real life is occurring on a background of Raleigh scattering – spectral densities at those blue wavelengths for the rainbow are reduced through scattering so appearances are going to be deceiving.

Hahaha, you did warn that it might be a bit pedantic, I think this one is a little bit for me

I hope you are doing well, I still tell people about the letter you sent with Mischa! That and the cockcopter. Also, the ninjas came in very handy in the defence. What research are you up to at the moment? Do you have anything I can read? Behrens.paul@gmail.com is the address if you have time to send something.