Question

12.(d) Light of wavelength 4.5×10⁻⁷m is incident on a metal resulting in the emission of photoelectrons. If the work function of the metal is 3.0×10⁻¹⁹J, calculate the:
(i) frequency of the incident light; (ii) energy of the incident light; (iii) energy of the photoelectrons. [Speed of light = 3.0×10⁸ms⁻¹, h = 6.6×10⁻³⁴Js]

Accepted Answer

(i) f = c/λ = (3.0×10⁸)/(4.5×10⁻⁷) ≈ 6.67×10¹⁴Hz.
(ii) E = hf = 6.6×10⁻³⁴×6.67×10¹⁴ ≈ 4.4×10⁻¹⁹J.
(iii) Energy of photoelectrons = E − work function = 4.4×10⁻¹⁹ − 3.0×10⁻¹⁹ = 1.4×10⁻¹⁹J.

WAEC Physics 2018 Theory — Question 27

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