9. A freshly cleaned piece of zinc metal is placed on the cap of a negatively charged gold leaf electroscope and illuminated with ultraviolet radiation. Explain why the leaves of the electroscope collapse.
Explain why the leaves do not collapse when: (i) the zinc is covered by a piece of ordinary glass (ii) the zinc is illuminated with green light (iii) the electroscope is charged positively.
Calculate: (i) the threshold frequency of zinc (ii) the maximum kinetic energy of an emitted electron.
(9)
(15)
The zinc metal is illuminated with ultraviolet light of wavelength 240 nm. The work function of zinc is 4.3 eV.
(20) (Planck’s constant = 6.6 × 10–34 J s; speed of light = 3.0 × 108 m s–1; 1 eV = 1.6 × 10–19 J)
