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Parent questions: Do photons lose energy after radiation pressure is applied to a perfect reflector?

Since radiation loses energy to radiation pressure in a reflection, can the entire energy of a radiation be consumed through multiple reflections?

Radiation pressure lowers a photon's frequency. I asked separately if this could be used to convert all the photon's energy to kinetic energy.

Now the present question is, by using radiation pressure or not, is it possible to convert a photon's entire energy to kinetic energy in a straightforward way? By straightforward, I mean not using successive conversions like a solar panel and an electric motor, whatever, but doing it the most possible direct way.

Winston
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It can't be done through direct kinematic interactions unless you set up multiple reflections.

Your choices of direct kinematic interactions are inelastic or elastic.

In inelastic, all the energy of the photon goes into something else, often heat. You could conceivably instead drive a reaction (like exciting a molecule) and then recover the energy from that reaction. But that sounds like not what you're looking for.

The other choice is an elastic interaction. In that case, the photon must still exist and carry energy away from the collision. The lower the energy of the photon in your frame, the less of the fraction that it leaves with, but also the less energy that you can harvest from it.

BowlOfRed
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Yes, most of the energy in EM radiation can be converted to kinetic energy. Look up "photon piston" or photo-Carnot engine. https://en.m.wikipedia.org/wiki/Photo-Carnot_engine

S. McGrew
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Is there a way to convert directly most electromagnetic radiation to kinetic energy?

What comes to mind for me is the conversion of microwave frequency electromagnetic energy to kinetic energy when a microwave oven heats food. The frequency of the microwave photon is such that it increases the rotational kinetic energy of water molecules due to their dipolar nature (the alternating microwave electric field causes the water molecules to rotate to align with the field.) That rotational kinetic energy is quickly randomized as translational kinetic energy of the water molecules.

For a more detailed explanation, see this: http://hyperphysics.phy-astr.gsu.edu/hbase/mod3.html

Hope this helps.

Bob D
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