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if Monochromatic rays of some intensity fall on a metal plate placed on a rough horizontal surface at certain angle. Will the plate move if the plate is perfectly reflecting irrespective of the value of intensity??

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closed as unclear what you're asking by Bill N, Cosmas Zachos, freecharly, Kyle Kanos, Jon Custer Jan 24 '18 at 14:05

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  • $\begingroup$ Please...I need an answer to this question. $\endgroup$ – Carrick Jan 14 '18 at 18:08
  • $\begingroup$ Irrespective of intensity? Do a thought experiment: reduce your ray to just one photon. What happens then? $\endgroup$ – Cosmas Zachos Jan 14 '18 at 19:15
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    $\begingroup$ In space, where it is a vacuum, shining a torchlight can cause you to move in the other direction, due to photons emitted. $\endgroup$ – QuIcKmAtHs Jan 14 '18 at 22:12
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    $\begingroup$ The light will obviously cause the plate to move in space. I was just drawing a parallel above. $\endgroup$ – QuIcKmAtHs Jan 14 '18 at 22:15
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    $\begingroup$ Possible duplicate of How does the solar sailing concept work? $\endgroup$ – Kyle Kanos Jan 24 '18 at 11:21
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Let's say the plate is in the x-y plane, and the incident rays are in the x-z plane. If the plate is perfectly reflecting, all the incident light will maintain its x-momentum after reflection. The z-component of the momentum is reversed, so the plate experiences a downward force due to the light. But no force in the x or y directions. The plate will not move.

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