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JEE Main202229 Jul 2022Morning ShiftPhysicsDual Nature of MatterActual

The kinetic energy of emitted electron is E when the light incident on the metal has wavelength λ . To double the kinetic energy, the incident light must have wavelength:

Options

  1. Ah c E λ - h c
  2. Bh c λ E λ + h c
  3. Ch λ E λ + h c
  4. Dh c λ E λ - h c

Correct answer

B. h c λ E λ + h c

Step-by-step solution

Using Einstein's photoelectric equation, kinetic energy of an electron is E when the incident wavelength is λ is E = h c λ - ϕ           . . . 1 When kinetic energy doubles, then, 2 E = h c λ ' - ϕ       . . . 2 Subtracting 2 - 1 , we have E = h c 1 λ ' - 1 λ ⇒ λ ' = h c λ E λ + h c

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