page 13 16. A photon of energy 6·40 × 10−19 J is incident on a metal plate. This causes photoemission to take place. The work function of the metal is 4·20 × 10−19 J. The maximum speed of the photoelectron is A 1·19 × 106 m s−1 B 9·60 × 105 m s−1 C 6·95 × 105 m s−1 D 6·79 × 105 m s−1 E 4·91 × 105 m s−1. 17. Waves from two coherent sources, S1 and S2, produce an interference pattern. Maxima are detected at the positions shown. maximum maximum maximum maximum maximum maximum S2 S1 central maximum P The wavelength of the waves is 28 mm. For the third minimum at P the path difference (S2P - S1P) is A 42 mm B 56 mm C 70 mm D 84 mm E 98 mm. [Turn over