Show that the radiation pressure exerted by an EM wave of intensity I on a surface kept in vacuum is I/c.
pressure on surface due to particle nature of wave P=AF force = Rate of change of momentum If mass (m) of radiant particle for wave of velocity c then E=mc2 E=U (let) U=mc.c U=p.c where momentum p=mc Now differentiating w.r t time (t) we get dtdU=c.dtdp c1.dtdU of AF=A1.c1.dtdU Pressire (P) on surface due to e.m wave radiation and p=AF p=c1[AdtdU] We know that intensity of radiation is equal to the radiant energy (U) falling on unit surface per second ∴ I=A1.dtdU or P=c1 Hence proved
