JAMB Physics 2019 Objective — Question 1

Question 1 of 40 from the Joint Admissions and Matriculation Board (JAMB) Physics 2019 Objective paper, with the correct answer and a full explanation.

A particular metal has a work function of 2.0eV. If light of wave-length 151nm falls on it, the maximum energy of the photo electron emitted is

A. 3.2×10⁻¹⁹J
B. 9.972×10⁻¹⁹JCorrect
C. 1.3172×10⁻¹⁸J
D. 1.51×10⁻¹⁹J

Explanation

W₀=2.0eV=1.6×10⁻¹⁹×2=3.2×10⁻¹⁹J. Energy of light E=hc/λ=(6.63×10⁻³⁴×3×10⁸)/(1.51×10⁻⁷)=1.3172×10⁻¹⁸J. Kinetic energy = E−W₀ = 1.3172×10⁻¹⁸−3.2×10⁻¹⁹ = 9.972×10⁻¹⁹J.

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