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Photo-electrons are produced by from a metal surface using a radiation of wavelength 6561 A ∘ . These photo-electrons, when made to enter a uniform magnetic field of intensity 3 × 10 − 4 T , move along different circular paths with a maximum radius of 10 mm , then the work function of the metal is close to

Options

  1. A3 . 1 eV
  2. B0 . 1 eV
  3. C2 . 1 eV
  4. D1 . 1 eV

Correct answer

D. 1 . 1 eV

Step-by-step solution

KE max = E - ϕ = 12400 λ ( in A ) - ϕ ( in eV ) ∴ r = 2 mKE eB KE max = r 2 e 2 B 2 2 m = r 2 eB 2 2 m (in J ) ∴ ϕ = 12400 6561 - r 2 eB 2 2 m = 1 . 1 eV

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