Cut off potential for a metal in photoelectric effect for light of wavelength lambda_(1), lambda_(2) and lambda_(3) is found to be V_(1),V_(2) and V_(3) volts , If V_(1),V_(2) and V_(3 are in Arithmetic progression then lambda_(1),lambda_(2) and lambda_(3) will be in Cut off potential for a metal in photoelectric effect for light of wavelength lambda_(1) [...]