(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 .