12   16 In an investigation of the photoelectric effect, electromagnetic radiation of frequency f was directed onto a metal plate. The maximum kinetic energy E of the photoelectrons emitted from the metal plate was determined. The procedure was repeated for a range of frequencies. The graph shows how E depended upon f. 2.0 1.5 1.0 0.5 0.0 50 110 100 90 80 70 60 f / 1013 Hz E / eV (a) Determine a value for the Planck constant, h, in J s. (4) .................................................................................................................................................................................................................................................. .................................................................................................................................................................................................................................................. .................................................................................................................................................................................................................................................. .................................................................................................................................................................................................................................................. .................................................................................................................................................................................................................................................. .................................................................................................................................................................................................................................................. .................................................................................................................................................................................................................................................. h = ...................................................... J s Turn over 13   (b) The table gives data for different metal surfaces. Metal surface Work function / eV Caesium 2.0 Calcium 2.9 Magnesium 3.7 Deduce which metal was being used in the investigation. (3) .................................................................................................................................................................................................................................................. .................................................................................................................................................................................................................................................. .................................................................................................................................................................................................................................................. .................................................................................................................................................................................................................................................. .................................................................................................................................................................................................................................................. .................................................................................................................................................................................................................................................. .................................................................................................................................................................................................................................................. (Total for Question 16 = 7 marks)