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Thread: photo-electric cells + colour?

  1. #1 photo-electric cells + colour? 
    Forum Freshman
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    Hi

    Question please!

    Photo-electric cells detect light, but can they read colour?

    Seeing that colour vibrates, can the different frequencies of different colours be detected?

    Many thanks

    Phaeton


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  3. #2  
    Forum Isotope
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    Quote Originally Posted by phaeton View Post
    Hi

    Question please!

    Photo-electric cells detect light, but can they read colour?

    Seeing that colour vibrates, can the different frequencies of different colours be detected?

    Many thanks

    Phaeton
    Photodetectors are sensitive to a variety of wavelengths (colors). The specific wavelengths to which they are sensitive depend on the composition of the detector, as well as the presence or absence of filters. The camera in your cellphone, for example, is generally sensitive to wavelengths ranging from the near-infrared to violet. Red, green and blue filters on top of the sensors resolve an image into separate RGB components to produce a full-color sensor.

    Other, specialized detectors can sense both far shorter and far longer wavelengths, although generally not in one materials system. For example, x-ray sensors will generally not function well (or at all) with longer wavelengths, and vice-versa.


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  4. #3  
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    Dear tk421

    Thank you - that is quite amazing!

    Phaeton
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  5. #4  
    Time Lord
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    Yeah. It's really fairly simple.

    For a digital camera, usually they put the photo-electric sensors in groups of three, grouped next to each other, with one having an approximately red filter over it, another with an approximately green filter over it, and the other with an approximately blue filter over it. The sensors themselves are the same, but the filters (just colored glass, really) cause them to see proportionally different amounts of light, depending on what color the light is. If it's red, then the red sensor will see more light than the blue or green sensors see, and so the processor/chip/whatever just compares how bright the light is on each of the three sensors to know what color it is.
    Some clocks are only right twice a day, but they are still right when they are right.
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