WAEC Physics 2013 Objective — Question 46
Question 46 of 50 from the West African Examinations Council (WAEC) Physics 2013 Objective paper, with the correct answer and a full explanation.
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The work function of a metal is 2.56×10⁻¹⁹ J. Calculate the frequency of a photon whose energy is required to eject from the metal an electron with kinetic energy of 3.0 eV. [1eV=1.6×10⁻¹⁹ J; h=6.6×10⁻³⁴Js]
- A. 5.56×10¹⁹ Hz
- B. 1.66×10¹⁹ Hz
- C. 1.12×10¹⁵ HzCorrect
- D. 8.42×10¹⁴ Hz
Explanation
Energy of photon = work function + K.E of electron = 2.56×10⁻¹⁹ + (3.0×1.6×10⁻¹⁹) = 7.36×10⁻¹⁹J. Frequency f = E/h = 7.36×10⁻¹⁹/6.6×10⁻³⁴ = 1.12×10¹⁵Hz.
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