Page 08 11. The table below shows the threshold frequency of radiation for photoelectric emission for some metals. Metal Threshold frequency (Hz) sodium 4·4 × 1014 potassium 5·4 × 1014 zinc 6·9 × 1014 Radiation of frequency 6·3 × 1014 Hz is incident on the surface of each of the metals. Photoelectric emission occurs from A sodium only B zinc only C potassium only D sodium and potassium only E zinc and potassium only. 12. Radiation of frequency 9·00 × 1015 Hz is incident on a clean metal surface. The maximum kinetic energy of a photoelectron ejected from this surface is 5·70 × 10−18 J. The work function of the metal is A 2·67 × 10−19 J B 5·97 × 10−18 J C 1·17 × 10−17 J D 2·07 × 10−2 J E 9·60 × 10−1 J.