Ultramicroscope is an instrument that enables a person to see such objects as fog drops, smoke particles, and paint pigments that float in liquids or gases. Such objects are called colloidal particles (see Colloid ). Objects as small as 5 nanometers in diameter can be seen with an ultramicroscope. One nanometer equals 1 billionth of a meter, or 1/25,400,000 of an inch.
The ultramicroscope consists of a compound microscope and a high-intensity light system. In most cases, the strong light originates from an arc lamp. The light is focused into a thin beam and directed at the particles from the side of the microscope. As the beam passes through the particles, it produces a cone of light because of the light-scattering effect of the particles. This phenomenon is called the Tyndall effect. The particles are observed by the light they scatter, rather than the light they reflect, which is used in conventional microscopy. The particles are viewed against a black background and appear as tiny bright dots of light, without structural detail. The first ultramicroscope was designed in 1903 by two German scientists, Richard Zsigmondy and Henry Siedentopf.
