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MHT CET20225 Aug 2022Morning ShiftPhysicsDual Nature of MatterActual

A photon of energy ' E ' ejects photoelectrons from a metal surface whose work function is W₀ . If this electron enters into a uniform magnetic field with induction ' B ' in a direction perpendicular to the field and describes a circular path of radius ' r ', then the radius is given by

Options

  1. A2 e (E-W₀ ) m B
  2. B2 (E-W₀ ) m e B
  3. C2 m (E-W₀ ) m B
  4. D2 m (E-W₀ ) e B

Correct answer

B. 2 (E-W₀ ) m e B

Step-by-step solution

Concept: Photoelectric effect and the motion of charge in a direction perpendicular to the magnetic field` The maximum kinetic energy K= m v^2 2 of a photo-electron is given by,' K=E-W₀ where, E is the energy of incident photon and W₀ is the work function of the metal. Therefore, the velocity of the photoelectron is: v= 2 (E-W₀ ) m The photoelectron undergoes uniform circular motion as its velocity is perpendicular to the magnetic field. On balancing magnetic force on moving charge with centrifugal force: q v B= m

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