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Q & A: Measuring the intensity of a laser

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Most recent answer: 02/03/2015
I'm doing a school science project on reflection and refraction of light. I'm seeing how different materials or substances react to a simple laser light. My problem is I need a cheap and easy way to measure the intensity of the laser light after it reflects, refracts or shines through. Thanks.
- Dan (age 13)
Virginia, USA

A PIN photodiode together with a standard digital voltmeter provides an easy, cheap way to measure light intensity. I think the diode should cost less than $10. You probably have a DVM around anyway. You want to pick a diode that works well for the particular color of your laser. If there's too much background light, you could get a little filter that transmits a narrow range of frequencies around the laser frequency, but those cost about $50. In case the light is so bright that it would damage the diode, you could use some clip-on sunglass material to reduce the light hitting the diode. You could try both the current measuring and voltage measuring modes of the  DVM to see which works better for your diode.

Mike W.

(published on 02/03/2015)

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