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Since $\vec F=d\vec p/dt$ and light consists of photons which experience a change in their momentum when they are reflected off a surface it follows that some force must act on those photons at the surface. However, since photons have no mass and no charge it is not at all obvious what that force should be. Any ideas?

The Riddler
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    Take it the other day around : when a beam is reflected, it exerces a radiative pressure on the wall (which happens to be exactely the opposite of the force you are talking about). Where is this force coming from ? – Pen Mar 18 '17 at 00:12
  • The Wikipedia article on radiation pressure does not actually say what the force is: "The generation of radiation pressure results from the momentum property of photons, specifically, changing the momentum when incident radiation strikes a surface. The surface exerts a force on the photons in changing their momentum by Newton's Second Law. A reactive force is applied to the body by Newton's Third Law." – The Riddler Mar 18 '17 at 00:23
  • Think of it classically: what force causes, say, a transverse wave in a rope to reflect off of a fixed barrier? – probably_someone Mar 18 '17 at 02:44
  • The tension in the rope, which can be understood fundamentally in terms of electromagnetic forces. But I'm not sure if electromagnetic forces can affect photons. – The Riddler Mar 18 '17 at 15:35
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    @user5556984 photons are excitations in the electromagnetic field. Electromagnetic forces are the only forces that can affect photons. – Asher Mar 18 '17 at 16:53
  • Photons are force carriers for the electromagnetic force, I'm not sure if they can be affected by that force themselves. – The Riddler Mar 18 '17 at 17:19

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