A metal surface is illuminated with photons of energies E 1 = 4 eV and E 2 = 2.5 eV respectively. The ratio of maximum speeds of the photoelectrons in two cases is 2 . Work function of metal surfa

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A metal surface is illuminated with photons of energies E 1 ​ = 4 eV and E 2 ​ = 2.5 eV respectively. The ratio of maximum speeds of the photoelectrons in two cases is 2 . Work function of metal surface will be

TestHub · Accepted Answer

From Einstein's photoelectric equation, As KE = h f − ϕ 0 ​ ⇒ 2 1 ​ m v 1 2 ​ = 4 − ϕ 0 ​ ...(i) and 2 1 ​ m v 2 2 ​ = 2.5 − ϕ 0 ​ ...(ii) From Eqs. (i) and (ii), we get ∴ v 2 2 ​ v 1 2 ​ ​ = 2.5 − ϕ 0 ​ 4 − ϕ 0 ​ ​ or 4 = 2.5 − ϕ 0 ​ 4 − ϕ 0 ​ ​ ( as , v 2 ​ v 1 ​ ​ = 2 ) So, ϕ 0 ​ = 2 eV

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