In a photoelectric-effect experiment, the maximum kinetic energy of electrons is 3.0 eV. When the wavelength of the light is increased by 50%, the maximum energy decreases to 1.5 eV. What is the original wavelength of the light?
a) The original wavelength is halved
b) The original wavelength is doubled
c) The original wavelength is multiplied by 1.5
d) The original wavelength remains unchanged