The kinetic energy of emitted electron is E when the light incident on the metal has wavelength λ . To…

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:
  1. hcEλ-hc
  2. hcλEλ+hc
  3. hλEλ+hc
  4. hcλEλ-hc

Solution

Using Einstein's photoelectric equation, kinetic energy of an electron is E when the incident wavelength is λ is E=hcλ-ϕ     ...1

When kinetic energy doubles, then, 2E=hcλ'-ϕ   ...2

Subtracting 2-1, we have 

E=hc1λ'-1λ

λ'=hcλEλ+hc

Asked in: JEE Main 2022 (29 Jul Shift 1)

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