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Light Intensifier

  1. May 17, 2015 #1
    1. I am supposed to create a device that can intensify the light directed at a light intensity sensor. A small light bulb will be 25 cm away from the light sensor. My device is required to be 20cm long and placed in between the light bulb and the light sensor in order to make the light that is entering the light sensor to be more intense. How should my device look?

    I believe that by trapping the light through a tunnel and at the very end I could insert a magnifying glass as it is a converging lens. However, I am worried about the focal point. Is the focal point relevant? Should my magnifying glass be at a certain distance in order to intensify light or will it intensify the light regardless. I am allowed to use any disposable, recycable and household materials in order to create this device.
    Last edited by a moderator: May 19, 2015
  2. jcsd
  3. May 18, 2015 #2
    Since this is HOMEWORK you'll get design examples, selection and calculations are upto you.

    Use a pipe with standard magnifying lenses at both ends.
    The bulb should be at the focal point of the lens which will then allow the light to move parallely. This parallel light will hit the lens at the other end which will conc. it on the light sensor at its focal point.
    You can use a fibre optic cable for total internal reflection.


    amplification would require a much more complicated design.
    Last edited: May 18, 2015
  4. May 19, 2015 #3
    Thank you, however I am only allowed one lens. So currently, I have created a tunnel using aluminium foil with the lens at the very end. Therefore, my light bulb is approximately 20 cm away from the lens and the light rays emitted from the light bulb travel through the tunnel and refract upon reaching the lens. The lens is placed 5 cm away from the light sensor, will this device be successful?
  5. May 19, 2015 #4


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    Staff: Mentor

    Welcome to the PF.

    Do you know how to draw ray tracing diagrams? You can use that technique to figure out what the shape of the reflecting tunnel should be. You should also look at how different telescope designs are put together to see if that gives you other ideas.
  6. May 19, 2015 #5
    Listen Zoe If you HAVE to use only 1 lens remember that the standard lens conc only parallel light to its focal point. All other incident light angles will be deviated to nearabout.
    So reflection in the tube will carry the light to the lens but not hit it parallely. The light will therefore be conc but not all at the focal point.
    I would suggest removing the tube and using a parabolic mirror instead
    Last edited: May 20, 2015
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