An ultramicroscope is a

microscope A microscope () is a laboratory instrument used to examine objects that are too small to be seen by the naked eye. Microscopy is the science of investigating small objects and structures using a microscope. Microscopic means being invisi ...

with a system that lights the object in a way that allows viewing of tiny

particle In the physical sciences, a particle (or corpuscule in older texts) is a small localized object which can be described by several physical or chemical properties, such as volume, density, or mass. They vary greatly in size or quantity, from ...

s via

light scattering Scattering is a term used in physics to describe a wide range of physical processes where moving particles or radiation of some form, such as light or sound, are forced to deviate from a straight trajectory by localized non-uniformities (including ...

, and not light reflection or

absorption Absorption may refer to: Chemistry and biology *Absorption (biology), digestion **Absorption (small intestine) *Absorption (chemistry), diffusion of particles of gas or liquid into liquid or solid materials *Absorption (skin), a route by which s ...

. When the diameter of a particle is below or near the

wavelength In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats. It is the distance between consecutive corresponding points of the same phase on the wave, such as two adjacent crests, tr ...

visible light Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 t ...

(around 500

nanometer 330px, Different lengths as in respect to the molecular scale. The nanometre (international spelling as used by the International Bureau of Weights and Measures; SI symbol: nm) or nanometer (American and British English spelling differences#-re, ...

s), the particle cannot be seen in a

light microscope The optical microscope, also referred to as a light microscope, is a type of microscope that commonly uses visible light and a system of lenses to generate magnified images of small objects. Optical microscopes are the oldest design of microsc ...

with the usual methods of illumination. The ''ultra-'' in ''ultramicroscope'' refers to the ability to see objects whose diameter is shorter than the wavelength of visible light, on the model of the ''ultra-'' in ''

ultraviolet Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm (with a corresponding frequency around 30 PHz) to 400 nm (750 THz), shorter than that of visible light, but longer than X-rays. UV radiation ...

''.

Synopsis

In the system, the particles to be observed are dispersed in a liquid or gas

colloid A colloid is a mixture in which one substance consisting of microscopically dispersed insoluble particles is suspended throughout another substance. Some definitions specify that the particles must be dispersed in a liquid, while others extend ...

(or less often in a coarser suspension). The colloid is placed in a light-absorbing, dark enclosure, and illuminated with a convergent beam of intense light entering from one side. Light hitting the colloid particles will be scattered. In discussions about light scattering, the converging beam is called a "

Tyndall cone The Tyndall effect is light scattering by particles in a colloid or in a very fine suspension (chemistry), suspension. Also known as Tyndall scattering, it is similar to Rayleigh scattering, in that the intensity of the scattered light is invers ...

". The scene is viewed through an ordinary microscope placed at right angles to the direction of the lightbeam. Under the microscope, the individual particles will appear as small fuzzy spots of light moving irregularly. The spots are inherently fuzzy because light scattering produces fuzzier images than light reflection. The particles are in

Brownian motion Brownian motion, or pedesis (from grc, πήδησις "leaping"), is the random motion of particles suspended in a medium (a liquid or a gas). This pattern of motion typically consists of random fluctuations in a particle's position insi ...

in most kinds of liquid and gas colloids, which causes the movement of the spots. The ultramicroscope system can also be used to observe tiny nontransparent particles dispersed in a transparent solid or gel. Ultramicroscopes have been used for general observation of

aerosols An aerosol is a suspension of fine solid particles or liquid droplets in air or another gas. Aerosols can be natural or anthropogenic. Examples of natural aerosols are fog or mist, dust, forest exudates, and geyser steam. Examples of a ...

and

colloids A colloid is a mixture in which one substance consisting of microscopically dispersed insoluble particles is suspended throughout another substance. Some definitions specify that the particles must be dispersed in a liquid, while others extend ...

, in studying

, in observing ionization tracks in

cloud chamber A cloud chamber, also known as a Wilson cloud chamber, is a particle detector used for visualizing the passage of ionizing radiation. A cloud chamber consists of a sealed environment containing a supersaturated vapour of water or alcohol. An ...

s, and in studying biological ultrastructure.

History

In 1902, the ultramicroscope was developed by

Richard Adolf Zsigmondy Richard Adolf Zsigmondy ( hu, Zsigmondy Richárd Adolf; 1 April 1865 – 23 September 1929) was an Austrian-born chemist. He was known for his research in colloids, for which he was awarded the Nobel Prize in chemistry in 1925, as well as for c ...

(1865–1929) and

Henry Siedentopf Henry Friedrich Wilhelm Siedentopf (22 September 1872 in Bremen – 8 May 1940 in Jena) was a German physicist and pioneer of microscopy. Biography Siedentopf worked in Carl Zeiss company from 1899 to 1938. In 1907 he was nominated as the head ...

(1872–1940), working for

Carl Zeiss AG Carl Zeiss AG (), branded as ZEISS, is a German manufacturer of optical systems and optoelectronics, founded in Jena, Germany in 1846 by optician Carl Zeiss. Together with Ernst Abbe (joined 1866) and Otto Schott (joined 1884) he laid th ...

. Applying bright sunlight for illumination they were able to determine the size of 4 nm small

nanoparticle A nanoparticle or ultrafine particle is usually defined as a particle of matter that is between 1 and 100 nanometres (nm) in diameter. The term is sometimes used for larger particles, up to 500 nm, or fibers and tubes that are less than 10 ...

s in

cranberry glass Cranberry glass or Gold Ruby glass is a red glass made by adding gold salts or colloidal gold to molten glass. Tin, in the form of stannous chloride, is sometimes added in tiny amounts as a reducing agent. The glass is used primarily in exp ...

. Zsigmondy further improved the ultramicroscope and presented the immersion ultramicroscope in 1912, allowing the observation of suspended nanoparticles in defined fluidic volumes. In 1925, he was awarded the Nobel Prize in Chemistry for his research on colloids and the ultramicroscope. Later the development of

electron microscope An electron microscope is a microscope that uses a beam of accelerated electrons as a source of illumination. As the wavelength of an electron can be up to 100,000 times shorter than that of visible light photons, electron microscopes have a hi ...

s provided additional ways to see objects too small for light microscopy.

References

{{reflist category:Microscopes Optical microscopy techniques Scattering, absorption and radiative transfer (optics) Hungarian inventions

Synopsis

History

See also

References