The threshold frequency for a photosensitive metal is 3.3 $$ \times $$ 10¹⁴ Hz. If light of frequency 8.2 $$ \times $$ 10¹⁴ Hz is incident on this metal, the cut- off voltage for the photoelectron emission is nearly

In the Davisson and Germer experiment, the velocity of electrons emitted from the electron gun can be increased by

Photoelectric emission occurs only when the incident light has more than a certain minimum

Light of two different frequencies whose photons have energies 1 eV and 2.5 eV respectively illuminate a metallic surface whose work function is 0.5 eV successively. Ratio of maximum speeds of emitted electrons will be