WAEC Physics 2024 Objective — Question 25
Question 25 of 50 from the West African Examinations Council (WAEC) Physics 2024 Objective paper, with the correct answer and a full explanation.
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25. Light of energy 1.12x10^-18 J is incident on a metal of ejected electrons with maximum energy of 8.0x10^-19 J. Calculate the threshold frequency of the metal. [h=6.626x10^-34 Js]
- A. 4.8x10^14 HzCorrect
- B. 1.2x10^15 Hz
- C. 1.7x10^15 Hz
- D. 2.8x10^15 Hz
Explanation
E=Wo+K.E. Wo=E-K.E.=1.12x10^-18-8x10^-19=3.2x10^-19J. Wo=hfo. fo=Wo/h=3.2x10^-19/6.626x10^-34=4.83x10^14Hz.
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