Question

15(c)(ii) E = W0 + K.E. A certain metal of work function 1.6eV is irradiated with ultra-violet light of wavelength 3.6x10⁻⁷m. Calculate the maximum kinetic energy of an ejected electron in joules.

Accepted Answer

E = hf = hc/λ = W0 + K.E. Where h=6.6x10⁻³⁴Js, c=3.0x10^8m/s, λ=3.6x10⁻⁷m: hf = (6.6x10⁻³⁴x3.0x10^8)/3.6x10⁻⁷ = 5.5x10⁻¹⁹J.
W0 = 1.6eV = 1.6x1.6x10⁻¹⁹ = 2.56x10⁻¹⁹J (approx 2.50x10⁻¹⁹J per official key).
K.E. = hf - W0 = 5.5x10⁻¹⁹ - 2.50x10⁻¹⁹ = 2.9x10⁻¹⁹J.

WAEC Physics 2011 Theory — Question 37

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