ABSTRACT
Self-luminous hot bodies such as the sun and stars are called incandescent. All the other forms of light emission by objects are luminescence. Emission of light as a result of absorbed light radiation is known as photoluminescence. Here, the electrons of the object that absorb the light radiation first get excited and then revert back to ground state through the loss of vibrational energy which is externally seen as light emission. Fluorescent substances get excited when irradiated with high energy radiations of shorter wavelengths, such as UV, blue-violet, and blue, and emit low energy light of longer wavelengths such as green, yellow, and red, thus following Stoke’s Law. This difference in absorbed and emitted wavelengths is the basis for observation of fluorescence in fluorescence microscopy. Substances exhibiting fluorescence are called fluorophores or fluorochromes. Different fluorochromes have different spectral characteristics, as a result of differing electronic configurations.
