In semiconductors, two basic properties namely energy gap and refractive index mostly determine their optical and electronic operation. Refractive index of a material usually decreases with an increase in energy gap fostering an underlying relationship between these two fundamental quantities. There have been many attempts to correlate these two quantities with a suitable empirical or semi-empirical relation. The refractive index and energy gap of semiconductors represent two fundamental physical aspects thatcharacterize their optical and electronic properties. In the present work, I have investigated some of the optical and electronic properties of II-VI group semiconductors.The II-VI compounds are being extensively used in infrared detectors, ultra high speed bipolar transistors, optical fiber communications and advanced microwave devices. Thesematerials possess the appropriate direct band gap to produce light emitting diodes and lasers from blue to red wavelength.