Answer to Question 5

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(a) l = c/f = 3 108  m s-1 110.90 106 Hz = 2.71 m

(b) E = hf = 6.63 10-34 J s 110.90 106 Hz = 7.35 10-26 J

(c) no of photons per sec = power energy per photon = 100 W 7.35 10-26 J = 1.36 1027 s-1 = 1.4 1027 s-1 (2 s.f.)