70) In an experiment of photoelectric emission for incident light of 4000?A⁰, the stopping potential is 2V. If the wavelength of incident light is made 3000?A⁰, then stopping potential will be

71) Work function of tungsten and sodium are 4.4eV and 2.3 eV respectively. If threshold wavelength of sodium is 5460A⁰, then threshold wavelength of tungsten is

72) in photoelectric effect, the photoelectric current

73) If we consider electrons and photons of the same wavelength, then they will have the same

74) The work function of a metal is 4Ev. For emitting photoelectrons of zero velocity from the surface of this metal, the wavelength of incident light required must be