Let, consider a phototube having a cathode made of Sodium metal:
i) Determine the longest wavelength which will generate photoelectrons when no voltage is applied to the phototube?
ii) Determine the maximum kinetic energy of an electron when 400 nm light is incident on the cathode and no electric potential is positioned on the phototube?
iii) Determine how much reverse bias should be positioned on the phototube to prevent photoelectrons from being generated through 400 nm light?