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NEETPhysicsDual Nature of Matter

The work functions of three metals P, Q and R are 2.5 eV , 3.2 eV and 4.8 eV respectively. They are illuminated by a light of wavelength 310 nm . Which of these metals will emit photoelectrons, and what will be the maximum kinetic energy of the photoelectrons emitted from the metal having the lowest work function? (Take hc = 1240 eV nm )

Options

  1. AP and Q ; 1.5 eV
  2. BP only ; 1.5 eV
  3. CP and Q ; 0.8 eV
  4. DR only ; 0.8 eV

Correct answer

A. P and Q ; 1.5 eV

Step-by-step solution

First, calculate the energy of the incident photon using the formula E = hc . E = 1240 eV nm 310 nm = 4.0 eV For photoelectric emission to take place, the incident photon energy must be greater than or equal to the work function of the metal ( E ). Comparing E with the given work functions: _ P = 2.5 eV _ Q = 3.2 eV _ R = 4.8 eV > 4.0 eV (No emission) Thus, metals P and Q will emit photoelectrons. The metal with the lowest work function is P ( _ P = 2.5 eV ). According to Einstein's photoelectric equation, the maxi

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