58) Wavelength of light incident on a photo cell is 3000?A⁰, if stopping potential is 2.5 volts, then work function of the cathode of photo cell is

59) If the frequency of incident light on a certain metal is 8.2??10¹⁴Hz having threshold frequency of 3.3??10¹⁴?Hz , then cut off potential is

60) If light of frequency?10¹⁵?Hz is incident on sodium having work function 2.5eV,then energy of emitted photoelectrons is

61) Threshold wavelength for metal is 10,000 Å. If light of wavelength 5461Å is incident on it then stopping potential is 1.02 V, then value of Planck's constant is

62) An electron beam is subjected to a magnetic field of 2??10^?3T and an electric field of 3.4??10⁴Vm^?1?perpendicular to magnetic field. If the deviation of electrons is zero, the velocity of the beam is