• Question: How can we change the colour of some lights?

    Asked by anon-267549 on 10 Nov 2020.
    • Photo: Liza Sazonova

      Liza Sazonova answered on 10 Nov 2020:

      There are lots of ways to do this, and we do it all the time 🙂
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      The simplest is to take a white lamp and cover it with some cloth. If you take a red cloth, your light will be red. That’s how Christmas lights usually work – you just have white lamps in painted glass bulbs, you can check it for yourself!
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      This works because red paint has a cool physics property: it lets all /red/ light through, but it absorbs all the other light. So if you put a green light in a red-painted bulb you won’t see any light (in an ideal situation). The actual reason paint does this is quite complicated and comes from a combination of chemistry (what the paint is made from) and quantum physics!
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      This is the easiest way to change a color of light, but there are others if you meant something else 🙂

    • Photo: Jesse Dykes

      Jesse Dykes answered on 11 Nov 2020:

      If you look online you can find videos of LEDs being dipped in liquid nitrogen, which changes their colour. This kind of light source works by pushing electrons from one place to another, and changing the temperature affects how much energy can be taken from the electron, and therefore the colour of the light emitted

    • Photo: Daisy Shearer

      Daisy Shearer answered on 11 Nov 2020:

      The way that we change the colour of most lights is using a translucent material which a white light can travel through. Because of the colour of the material, only that wavelength is transmitted to your eyes. But we can also generate different colours of light, for example, you can get different colours of LED or laser. In these cases, we use some quantum physics knowledge to control the wavelength of light that is emitted. The wavelength (and hence colour) emitted depends on a property called the ‘band gap’ of the material.

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