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The work function of a metal is in the range of 2 eV to 5 eV . Find which of the following wavelength of light cannot be used for photoelectric effect. (Consider, Planck's constant = 4 × 10 − 15 eV-s , velocity of light =3 × 10 8 m s -1 )

Options

  1. A510 nm
  2. B650 nm
  3. C400 nm
  4. D570 nm

Correct answer

B. 650 nm

Step-by-step solution

Given that, 2 e V ≤ ϕ ≤ 5 e V Wavelength corresponding to minimum and maximum values of work function are λ m a x = h c E = 4 × 10 - 15 × 3 × 10 8 2 = 6 × 10 - 7 m = 600 n m And λ m i n = h c E = 4 × 10 - 15 × 3 × 10 8 5 = 2.4 × 10 - 7 m = 240 n m Clearly wavelength range would be 240 ≤ λ ≤ 600 Thus, wavelength 650 nm is not suitable for photoelectric effect.

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