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4
votes
1answer
385 views

Diffraction Pattern on LCD Screen

I was up late working with my red LED headlamp on and when I was looking at the black part of my LCD (Apple Retina Macbook Pro) screen I noticed this interesting diffraction pattern. I'm confused ...
62
votes
5answers
6k views

What challenges needed to be overcome to create (blue) LEDs?

In light of today's announcement of the 2014 Nobel laureates, and because of a discussion among colleagues about the physical significance of these devices, let me ask: What is the physical ...
2
votes
0answers
90 views

Where does an LED use energy other than emitting light?

I have a quantum formula describing what kind of photon should be emitted by an LED depending on its voltage. Of course the colour is depending on the material, but every type of LED also needs its ...
1
vote
1answer
191 views

What determines the forward voltage drop for a diode?

I have always had the idea that the forward voltage drop in a semiconductor diode was related in a simple way to the bandgap energies in the semiconductor. However this is apparently not the case: ...
0
votes
3answers
248 views

How to generate Red light from a Blue-Dominated Spectrum [closed]

I have a white LED light source, the spectrum of which looks as follows --- I want to filter out red light from this white LED source. But as you can see the spectrum dwindles in the red zone. And ...