(c) An e.m. wave exerts pressure on the surface on which it is incident. Justify. 

Answer

An EM Wave is composed of photons which have both energy (hv) and momentum (ƛ/h).

  • We know that Pressure = Force per unit area.
  • Force = Change in momentum per unit time.
  • Therefore, Pressure = Δp/A Δt
  • That is, pressure is exerted on surfaces due to a change in momentum .
  • When an EM wave strikes a surface, its momentum is either absorbed or reflected , leading to a sudden change in momentum

This change in the momentum of EM Waves exerts pressure on surfaces .

ELECTROMAGNETIC WAVE PROPAGATION.jpg

 

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