page 11 14. Electromagnetic radiation of frequency 9.0 × 1014 Hz is incident on a clean, negatively charged metal surface. The work function of the metal is 6.1 × 10−19 J. There is no photoelectric emission from this metal caused by this radiation. This is explained by the fact that A photoemission can only occur from a positively charged metal surface B the wavelength of the incident radiation is too short C the frequency of the incident radiation is less than the threshold frequency of this metal D the work function of the metal is less than the energy of the incident photons E the number of photons per second incident on the surface of the metal is too low. 15. A ray of monochromatic light is incident on a grating. An interference pattern is observed on the screen. monochromatic light grating screen 29° 29° The angle between the central maximum and the maximum observed at the edge of the screen is 29°. The wavelength of the light is 605 nm. The separation of the slits on the grating is 5.0 × 10−6 m. The total number of maxima observed on the screen is A 4 B 7 C 8 D 9 E 15. [Turn over