Radiometer and Laser Light
I would like to know if a radiometer will spin if exposed to laser
light. Why? Why not?
I do not have the resources to test this out, but I cannot think of
any reason why laser light would not cause a radiometer to spin. The black
faces of the vanes will absorb laser light just like any other light,
and become warmer than the bright faces. And it is that difference in
temperature that makes the radiometer spin (please see answer to #628).
Of course, if the laser beam is kept trained on just one of the vanes,
it will probably take longer for rotation to begin than if, say, sunlight
is used (I would be interested to know how long, if any, delay there is!)
Of course, you also have to consider the total energy deposited on
the radiometer vane. Remember that a laser has a high energy for a specific
wavelength but NO energy anywhere else in the spectrum. Light from the
sun has low energy at all wavelengths. The net result is you may be
putting a lot more energy onto the radiaometer vanes with a 50 Watt light
bulb than with a 100 mW He-Ne laser. A 50 Watt laser would work better
than a 50 W bulb but would cost 10's of thousands of dollars.
gregory r bradburn
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Update: June 2012