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NEETPhysicsDual Nature of Matter

The work functions of four metals P, Q, R and S are 2.1 eV, 2.8 eV, 3.4 eV and 4.5 eV respectively. If monochromatic light of wavelength 400 nm is incident on each of them, which of these metals will exhibit photoelectric emission? (Take hc = 1240 eV nm)

Options

  1. AR and S only
  2. BP only
  3. CP, Q and R only
  4. DP and Q only

Correct answer

D. P and Q only

Step-by-step solution

The energy of an incident photon is given by E = hc . Substituting the given values: E = 1240 eV nm 400 nm = 3.1 eV . For photoelectric emission to occur, the energy of the incident photon must be greater than or equal to the work function of the metal ( E ). Comparing the incident photon energy ( E = 3.1 eV ) with the given work functions: For P: 3.1 eV > 2.1 eV (Emission occurs) For Q: 3.1 eV > 2.8 eV (Emission occurs) For R: 3.1 eV For S: 3.1 eV Therefore, only metals P and Q will exhibit photoelectric emission.

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