A photon of wavelength 4 × 10-7 m strikes on metal surface; the work function of the metal being 2.13 eV. Calculate
(i) The energy of the photon,
(ii) The kinetic energy of the emission
(iii) The velocity of the photoelectron. (Given 1 eV = 1.6020 × 10-19 J).
A photon of wavelength 4 × 10-7 m strikes on metal surface; the work function of the metal being 2.13 eV. Calculate
(i) The energy of the photon,
(ii) The kinetic energy of the emission
(iii) The velocity of the photoelectron. (Given 1 eV = 1.6020 × 10-19 J).
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1 Answer
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(i) Energy of photon (E) = hc / λ
= (6.626 × 10-34 Js) x (3 × 108 m s-1) / (4 × 10-7 m) = 4.969 x 10-19 J
Since, 1.6020 × 10-19 J= 1 eV
So, 1 J= (1 eV) / (1.6020 × 10-19 J)
Hence, 4.969 x 10-19 J = (1eV) x (4.969 x 10-19 J) / (1.602 x 10-19 J) = 3.1 eV
(ii) Kinetic energy of emission = Energy – work function
= (3.1 – 2.13) = 0.97 eV
(iii) Kinetic energy of emission = 0.97 eV
=> ½ mv2= 0.97 eV = 0.97 x 1.602 x 10-19 J = 0.97 x 1.602 x 10-19 kg m2 s-2
=> v2 = (2 x 0.97 x 1.602 x 10-19 kg m2 s-2 ) / (9.1 x 10-31 kg) = 0.34 x 1012 m2 s-2
=> v = (0.34 x 1012 m
...more
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