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A plate of mass `10 gm` is in equillibrium in air due to the force exterted by light beam on plate. Calculate powder of beam. Assume plates is perfectly absorbing. |
Answer» Since plate is in air, so gravitational force will act on this `F_("gravitaional")=mg` (dowmward) `=10xx10^(-3)xx 10` `10^(-1)N` for the equilibrium force exterted by light beam should be equal to `F_("gravitational")` `F_("Photon")=F_("gravitaional")` Let power of light beam be `P` `:. F_("photon")=(P)/(c )` `:. (P)/(c )=10^(-1) P=3.0xx10^(8)xx10^(-1)` `P=3xx10^(7)W` |
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