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Q & A: inducing current with light

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Most recent answer: 01/05/2013
Q:
If light is an excitation in the electromagnetic field, is it possible to induce a current in a wire using light?
- David (age 18)
Oklahoma
A:
The direct process you may be thinking of, using the electric field of the light to pull the electrons in the wire around, doesn't work because visible light is too high-frequency. The electrons would just jiggle back and forth a tiny amount.

Lower frequency electromagnetic waves do exactly what you want, however, for example in a radio antenna. Visible light can be used to induce currents in a slightly more indirect way. The light can knock electrons off the surface of the metal, and they can then be gathered on another piece of metal, giving a current if the circuit is completed. This is called the photoelectric effect. However, it can't be pictured accurately using classical electromagnetism, but requires a quantum description.

Mike W.

(published on 01/05/2013)

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