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Measuring Light Intensity with LEDs: Emission, Transmission, Reflection and Absorption

Although these instruments cannot measure actual light magnitudes, they can be used to measure the percentage of reflectance, transmittance, and absorption of light from an object.

What to Do...

  1. Determine that the object does not emit light (test in dark room).

  2. Measure the voltage generated by incoming light (use sunlight).

  3. Measure the voltage being reflected off the object.

    The percent of light reflected is the voltage from reflected light / voltage from incoming light.

  4. If you can get behind the object, say it is a leaf or a piece of paper or fabric, measure the voltage of light traveling through the object.

    The percent of light being transmitted through the object is the voltage from transmitted light / voltage from incoming light.

  5. The light being absorbed from the object is

    Light absorbed = 100% - %reflected - %transmitted

    When the light source is accessible, measure a  set distance from the object so you can compare the intensity of emitted light.
When the light source is accessible, measure a 
set distance from the object so you can compare
the intensity of emitted light.