Q. Why is the color of the light different between an electric bulb and fluorescent light?

A. Edison of the United States invented the electric bulb in 1879. In the beginning, for the part that emits light (filament) charred string and charred Kyoto-produced bamboo were used. However, the brightness was low and life short. Tungsten has been used for the filament since around 1910 and argon gas was inserted inside the bulb to make the life of the filament longer. When an electric current flows through tungsten, it heats up to about 3,300 degrees Centigrade and the light that is produced at this temperature shows as a reddish light. With a fluorescent light, the inside of the glass tube is coated with fluorescent paint and mercury is inserted. When electrical current is applied, the mercury becomes a gas and produces ultraviolet rays. The fluorescent paint absorbs these ultraviolet rays and produces something like transparent light. Light produced by fluorescent paint absorbing some energy, for example, is called luminescence. By the way, it is the same kind of luminescence as when a firefly and noctiluca emit light.