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I Am Fascinated By Physics

The voltage drop across an LED seem to be directly proportional to the colour (energy) of the emitted light. e.g. red LEDs (wavelength c.660nm)have a voltage drop of about 1.8v and blue LEDs (wavelength c.450nm) about 3.3v.

If a LED needs 3.3v to emit blue light, how can a white LED (which must have a blue component) operate on only 3v?

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Tastyfrzz · 61-69, M

Higher frequencies /shorter wavelengths require more energy. I suspect an x-ray emitting LED would require a lot of voltage drop. Basically then you are just arcing across a gap.

rob19 · M

@Tastyfrzz Yes, I follow that. What I don't really understand is why a blue LED needs 3.3v but a white LED (which has a blue component) can do it with only 3v.

Tastyfrzz · 61-69, M

Intensity of the blue is diminished???

rob19 · M

@Tastyfrzz The brightness can be considered the number of photons per unit time, not the energy of the individual photon.

Tastyfrzz · 61-69, M

But you can plot the intensity by frquency. E=hv where h is plancks constant and v = frequency.

rob19 · M

@Tastyfrzz That's the energy (colour) of the individual photons. The intensity is the number of photons.