Ways of altering wavelength of electromagnetic radiation...

[Ruken]

@Nava

Maybe in DC… “we all”, seriously?

I don’t understand you.

[komolono]

If I could “draw” a nanoscale pattern of atoms I would see a corresponding color - yes/no?

[Malacandra]

@Nava

Maybe in DC… “we all”, seriously?

No, not “we all” - he said “(we start) (all our plants)…” (parentheses added to show parsing)

[komolono]

Am I talking about this

Structural coloration

tructural coloration?

[am77494]

As a followup question, from my highschool physics, I understood that the wavelength of all colors changed when they entered a different medium - like light travelling through water or glass. The frequency remained unchanged and hence the “reduced velocity of light” (c/v = μ) maintained the relationship v=ωλ

Did I understood it correct ? (I understand that the velocity of light here is the group velocity)

[Mangetout]

@CalMeacham

It’s not Blue and Red – it’s a relatively narrow blue LED (although the spectrum given looks rather broad) and a broad phosphor that covers a lot of wavelengths. By itself, I believe the phosphor looks kind of yellow. The combination of the two gives you a sort of bluish white.

Thought so - thanks.

I think they use them in a lot of those auto headlights that are an annoyingly bluish color.

I think those are actually mostly HID lamps.

The thing is, there are lots of phosphors you can use. Companies like Osram/Sylvania have vast “libraries” of such phosphors, and can give you all sorts of color balance. But the generic “white” LED available today from electronics suppliers still tends to be this awful soul-less bluish white. I’ve seen Osram’s “warm” phosphors that give you something closer to an incandescent lamp, but they’re not generally out on the market. I think the best thing companies like Osram could do would be to make such LEDs more widely available – it would do a lot to alter the public perception of what LEDs can look like.

Concur. I’ve got ‘warm white’ LED lighting in my kitchen and it’s quite lovely - to the human eye, pretty much indistinguishable from halogen incandescent.
It doesn’t work very well as the solo light source for photography, but none of its incandescent or fluorescent predecessors did either.

[CalMeacham]

@am77494

As a followup question, from my highschool physics, I understood that the wavelength of all colors changed when they entered a different medium - like light travelling through water or glass. The frequency remained unchanged and hence the “reduced velocity of light” (c/v = μ) maintained the relationship v=ωλ

Did I understood it correct ? (I understand that the velocity of light here is the group velocity)

You’re quite right. If you didn’t have a change in wavelength, there’d be a disconnect at the interface between the incoming and outgoing waves. Have a look at this animation from the Wikipedia page on Snell’s Law:

File:Snells law wavefronts.gif

The thing is, of course, that you’ll never see this shift in wavelength. As soon as the light comes out of the second medium into the first, the wavelength shifts back. No matter what medium it passes through, shifting wavelengths at every interface, it shifts back to the wavelength it has at the original medium when it goes back there.

Aha! you say – I’ll take it directly from one of those other media into my detector, or my eye, so it doesn’t have to go back out into the air! But it doesn’t matter – the shift as the light goes into your detector (or your eye) will mean that the wavelength is exactly what it would be in that detector (or your eye) if it went in directly from the air.