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Questions tagged [light-emitting-diodes]

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3
votes
2answers
191 views

Can zinc nitride be used as light emitting material?

I cannot manage to find any journal papers about the applicability of zinc nitride as active layer of an light emitting diode (LED). But certain papers got mention that zinc nitride with a direct ...
2
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3answers
418 views

How to smooth the spectrum of a light source?

Could somebody please tell me if there's a reasonably cheap substance or device can I use to smooth the spectrum of a light source? For example, if the spectrum has spikes as in the blue graph below, ...
9
votes
2answers
903 views

Could anyone help explain this current voltage graph for an LED in liquid nitrogen?

I've been doing my coursework investigating LEDs at various temperatures and I've come across an interesting phenomenon which nobody I've asked has been able to explain thoroughly - wheras at room ...
2
votes
2answers
1k views

Why would mode-hopping occur as the current is changed?

If some diode laser is given an input current, why should we see mode-hopping if the current is changed?
-1
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2answers
150 views

Speed of the light, is it everywhere light?

I have studied Electronics Engineering and of course the LED. I was wondering that they claim that the speed of light is $3\cdot10^8$ m/s, but do they claim the speed of the light of the sun rays ? ...
1
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0answers
62 views

Where does the reverse current come from in a organic semiconducting diode?

Unlike traditional inorganic diodes, organic semiconducting materials hold few thermally exited free carriers under room temperature, so the reverse current should be small if pinholes of the films is ...
3
votes
1answer
2k views

Is a 3 LED flashlight brighter than a single LED one? (same LEDs, same power through each LED)

Say I have one LED in a flashlight, it produces some light. Now, if I have 3 of those LEDs in the same flashlight, each LED receiving the same amount of energy than the single LED was receiving in ...
1
vote
2answers
792 views

Building a LED lamp, which is the brightest? 3 LEDs of 2500 mcd or 1 LED of 6000 mcd?

I want to build the brightest lamp, for it to be seen at daylight, should I use 3 2500 mcd LEDs or 1 6000 mcd? And also Why?
3
votes
0answers
1k views

Increase in Wavelength of an LED immersed in liquid nitrogen

"Hi, I've been working on an experiment where I dip LEDs into liquid nitrogen and note the color change. All online sources I've seen predict that the wavelength of the light emitted by the LED will ...
15
votes
6answers
2k views

Can someone explain the science behind MIT's 230% efficient LEDs?

I was reading Gizmodo the other day and I didn't quite understand the Physics behind this. Could anybody shed some light on how this effect actually works?
1
vote
3answers
1k views

Intensity distribution of a LED light source

The light source: 190 high power LEDs in NIR. I have the datasheet of the LED. I want to make a graph showing the spatial distribution, and to measure the intensity of the beam on the whole field of ...
1
vote
1answer
627 views

Does interchangeable wavelength LED exist in NIR?

Does exist a led material that allows to interchange the emitted wavelength in near IR spectrum?
13
votes
3answers
5k views

LED Thermal Modeling (How to solve heat equation with constant heat source)

I have a mechanical design with LEDs that generate heat. I want to estimate the temperature at the LED junction vs. time, but especially at steady state. Knowing the LED voltage drop and current, I ...
6
votes
1answer
5k views

How to determine divergence of a LED source from a single biconvex lens

I'm trying to determine the divergence angle of light from a single lens that is completely illuminated by a high power LED. Most optics textbooks only deal with imaging optics and I'm having a hard ...
10
votes
8answers
19k views

Why is a 1mW laser dangerous?

In our Physics lab we have a 1 milliwatt (0.001W) helium neon laser. Despite the low power, we were cautioned not to even look at reflections of the beam as it could cause permanent eye damage - why ...
5
votes
4answers
9k views

Can light emitting diodes be used to generate UV wavelengths?

I don't know much about light-emitting diodes, but I imaging if you had a panel of RGB diodes you could produce any wavelength of color within the visible light spectrum. However, if I also wanted to ...