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A metal exposed to light of wavelength 800 nm and emits photoelectrons with a certain kinetic energy. The maximum kinetic energy of photo-electron doubles when light of wavelength 500 nm is used. The work function of the metal is (Take h c = 1230 eV - nm ).

Options

  1. A1 . 537 eV
  2. B2 . 46 eV
  3. C0 . 615 eV
  4. D1 . 23 eV

Correct answer

C. 0 . 615 eV

Step-by-step solution

According to Einstein's photoelectric equation k m a x = h c λ - ϕ ⇒ k 1 = 1230 800 - ϕ               . . . 1 And ⇒ k 2 = 1230 500 - ϕ Since, k 2 = 2 k 1 ⇒ 2 k 1 = 1230 500 - ϕ         . . . 2 Eliminating k 1 from (1) and (2) we get 0 = 1230 500 - 1230 400 + ϕ ⇒ ϕ = 0 . 615   eV

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