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


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 .



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Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 14 years. He provides courses for Maths, Science, Social Science, Physics, Chemistry, Computer Science at Teachoo.