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KVPY2020PhysicsDual Nature of Matter

A zinc ball of radius, R = 1   cm charged to a potential - 0 . 5   V . The ball is illuminated by a monochromatic ultraviolet ( U V ) light with a wavelength 290 nm . The photoelectric threshold for zinc is 332 nm . The potential of ball after a prolonged exposure to the U V is

Options

  1. A- 0 . 5   V
  2. B0   V
  3. C0 . 54   V
  4. D0 . 79   V

Correct answer

C. 0 . 54   V

Step-by-step solution

ϕ = 12431 3320 = 3 . 74 eV ε = hc λ = 12431 2900 = 4 . 28 eV ( KE ) max = 4 . 28 - 3 . 74 = 0 . 54 eV Initially sphere is negatively charged so e - will go easily then potential becomes O . After that as e - will leave the potential will increase till it reaches the stopping potential value, V 0 e V 0 = 0 . 54 eV V 0 = 0 . 54   V

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