Burnt filament of a light bulb. Coloured Scanning Electron Micrograph (SEM) of the double coiled tungsten wire filament of a light bulb, after burning out. The broken coiled filament lies beside the wire posts of the light bulb. Tungsten is a heavy metal with an extremely high melting point and thus widely used in light filaments. With repeated use, however, the tungsten wire eventually breaks ending the life of the light bulb. Magnification: x21 at 6x7cm size. x58 at 7x8 inch size.