Light of wavelength 4000 A is incident on a metal plate where work function is 20 eV. The maximum kinetic energy of the emitted photoelectrons would be
(a) 2 eV
(b) 1.5 eV
(c) 1.1 eV
(d) 0.5 eV

The ground state energy of H-atom is 13.6 eV. The energy needed to lonise H-atom from its second excited state is
(a) 1.51 eV
(b) 3.4 eV
(c) 13.6 eV
(d) 12.1 V