In the phenomenon of electric discharge through gases at low pressure, the coloured glow in the tube appears as a result of

A particle of mass 1 mg has the same wavelength as an electron moving with a velocity of 3 $$ \times $$ 10⁶ m s^$$-$$1. The velocity of the particle is

The work function of a surface of a photosensitive material is 6.2 eV. The wavelength of the incident radiation for which the stopping potential is 5 V lies in the

Monochromatic light of frequency 6.0 $$ \times $$ 10¹⁴ Hz is produced by a laser. The power emitted is 2 $$ \times $$ 10^$$-$$3 W. The number of photons emitted, on the average, by the source per second is