Light sources can be either natural or artificial. Sun is the primary source of natural light, and lightbulbs or lamps are the artificial sources. Light is a form of electromagnetic energy that, in the case of natural light, comes from the sun as the source and, in case of artificial light, illuminates via energy from another source. No matter what the source, light has an impact on life on earth as a whole. Natural light consists of electromagnetic energy generated from the source; it contains a healthy spectrum of colors and wavelengths well suited for life on earth. Artificial light uses another energy source to generate light that is not as versatile as natural light and has a detrimental effect on plant and animal life when exposed for prolonged periods. Moderate exposure to all aspects of natural light is ideal for most life on earth; the same does not apply to artificial light, which generally serves a purpose of illumination during darkness. (Source)