Electrons are emitted with zero velocity from a metal surface when it is exposed to radiation of
wavelength 6800 Å. The work function (W0 ) of the metal is:
1. 3.109 x 10-20 J
2. 2.922 x 10-19 J
3. 4.031 x 1019 J
4. 2.319 x 10-18 J
When electromagnetic radiation of wavelength 300 nm falls on the surface of sodium, electrons are emitted with a kinetic energy of 1.68 ×105 J mol–1. The minimum energy needed to remove an electron from sodium and the maximum wavelength that will cause a photoelectron to be emitted are respectively:
1. 2.31 × 105 J mol–1, 517 nm
2. 23.1 × 105 J mol–1, 517 nm
3. 3.31 × 105 J mol–1, 417 nm
4. 33.1 × 105 J mol–1, 417 nm