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JEE Main20208 Jan 2020Morning ShiftPhysicsDual Nature of MatterActual

When photon of energy 4.0 e V strikes the surface of a metal A , the ejected photoelectrons have maximum kinetic energy T A e V and de-Broglie wavelength λ A . The maximum kinetic energy of photoelectrons liberated from another metal B by photon of energy 4.50 e V is T B = T A - 1.5 e V . If the de-Broglie wavelength of these photoelectrons λ B = 2 λ A , then the work function of metal B is:

Options

  1. A4 e V
  2. B2 e V
  3. C1.5 e V
  4. D3 e V

Correct answer

A. 4 e V

Step-by-step solution

Relation between de-Broglie wavelength and K.E. is λ = h 2 ( K E ) m e ⇒ λ ∝ 1 K E λ A λ B = K E B K E A ⇒ 1 2 = T A - 1.5 T A ⇒ T A = 2   e V ∴ K E B = 2 - 1.5 = 0.5   e V ϕ B = 4.5 - 0.5 = 4   e V

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