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I need your help as I am stuck and I dont know where to start. I have got four blue leds diode that come with dark blue led lights that I really want to get the same led colours for my 3 fans, but I have got no idea what the wavelength for that blue led lights.

Here is the pictures: https://i.sstatic.net/QKP39.png https://i.sstatic.net/wPAaS.jpg

I am not going to take out the LED diode yet until when I have been advice to do so. I think the wavelength is between 450nm to 470nm but I am not too sure. Do you know how I can find out what is the wavelength for that LEDS?

If you know how I can find out what wavelength for that blue leds, I would be very grateful for that useful information.

Qmechanic
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Robert Jones
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4 Answers4

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I work at a lab and we have access to a spectrophotometer like this one here https://oceanoptics.com/product/usb2000-custom/. You can get the spectrum of emitted light, its intensity by pointing LEDs towards the fiber optic cable. It is a trivial thing to do if you have access to any of such equipment. But these things are expensive I think.

bhagyesh
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If you have a decent enough camera, you could try to do a double slit experiment. But you’d have to be able to make fine slits. Or you could get a diffraction grating.

But if all you need is to match the wavelengths then you could perform the double slit experiment under same conditions except for the source LED and chose the ones whose interference pattern overlaps.

Superfast Jellyfish
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There is the plastic project Starlab spectroscope (instructions). Or you can make your own for free. For example with a piece of a CD-disk as a grating and a cereal box or similar.

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If you just want to compare the wavelengths of your 4 leds, an unused CD or DVD males a good reflection grating. Poke a small hole in a white sheet of paper. With the led and disk at least several inches from the hole on each side, let the beam from the hole hit the disk (at 90 degrees) and look for the first (or second) order reflection on the paper. You may need to work in the dark except for your led.

R.W. Bird
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