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प्रश्न
Show that the radiation pressure exerted by an EM wave of intensity I on a surface kept in vacuum is I/c.
उत्तर
Let us consider a surface exposed to electromagnetic radiation. The radiation is falling normally on the surface. Further, intensity of radiation is I and area of surface exposed to radiation is A.
E = Energy received by surface per second = I.A
N = Number of photons received by surface per second
N = `E/E_("photon") = (Eλ)/(hc) = (IAλ)/(hc)`
Let the surface is perfectly absorbing, `ΔP_("one photon") = h/λ`
⇒ F = `N xx ΔP_("one photon") = (IA)/c`
Also, Pressure P = `F/A = I/c`
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