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Reviewed CSCA Physics question · Hard

Light of frequency 1.5 x 10^15 Hz is incident on a metal with work function 3.0 eV. What is the maximum kinetic energy of emitted photoelectrons? (Planck constant h = 4.14 x 10^-15 eV·s)

  1. 3.2 eV
  2. 6.2 eV
  3. 9.2 eV
  4. 0.2 eV
Show the answer and explanation

Correct answer

A. 3.2 eV

Principle or equation

Photoelectric equation: K_max = h f - φ.

Why this answer is correct

Photon energy E = h f = (4.14 x 10^-15)(1.5 x 10^15) = 6.21 eV. K_max = 6.21 - 3.0 = 3.21 eV ≈ 3.2 eV.

Example

If f=1.0e15, φ=2 eV, then K_max = 4.14 - 2 = 2.14 eV.

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