The ground state confinement energy and its associated wavelength as a function of radius for three different semiconductor quantum dots (QDs) were calculated using the Brus equation. The experimental observation of the size dependence on the band gap energy is in good agreement with the theoretical models for the semiconductor nanocrystals considered. The confinement of electrons in semiconductor quantum dots increases dramatically with decrease in its size (radius) and shows exponential dependence on wavelength of light emitted.