# An Em Wave Exerts Pressure on the Surface on Which It is Incident. Justify. - Physics

An em wave exerts pressure on the surface on which it is incident. Justify.

#### Solution

An em wave carries a linear momentum with it. The linear momentum carried by a portion of wave having energy U is given by p=U/c.Thus, if the wave incident on a material surface is completely absorbed, it delivers energy U and momentum p=U/c to the surface. If the wave is totally reflected, the momentum delivered is p=(2U)/c because the momentum of the wave changes from p to -p. Therefore, it follows that an em waves incident on a surface exert a force and hence a pressure on the surface.

Concept: Electromagnetic Waves
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