Leslie's cube is a device used in the measurement or demonstration of the variations in

thermal radiation Thermal radiation is electromagnetic radiation generated by the thermal motion of particles in matter. Thermal radiation is generated when heat from the movement of charges in the material (electrons and protons in common forms of matter) i ...

emitted from different surfaces at the same temperature.

Device

It was devised in 1804 by John Leslie (1766–1832), a Scottish mathematician and physicist. In the version of the experiment described by John Tyndall in the late 1800s, one of the cube's vertical sides is coated with a layer of gold, another with a layer of silver, a third with a layer of copper, while the fourth side is coated with a varnish of

isinglass Isinglass () is a substance obtained from the dried swim bladders of fish. It is a form of collagen used mainly for the clarification or fining of some beer and wine. It can also be cooked into a paste for specialised gluing purposes. The ...

. The cube is made from a solid block of metal with a central cavity. In use, the cavity was filled with hot water; the entire cube has essentially the same temperature as the water. The thermal detector (on the far right in the figure) showed much greater emission from the side with varnish than from any of the other three sides. In contemporary terms, the emissivities of shiny

metals A metal (from Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts electricity and heat relatively well. Metals are typical ...

are low. Isinglass is an organic glue, and has a much larger emissivity than the metals. Leslie's cube is still in use to demonstrate and measure the variations in emissivities for different materials. In the figure, the false color images (" thermographs") of a cube at about 55 °C were taken with an infrared camera; the black and white photographs are taken with an ordinary camera. The black face of the cube is highly emissive, as indicated by the reddish color of the thermograph. The mirror-like, polished face of the aluminum cube emits thermal radiation weakly, as indicated by the blue color. The reflection of the experimenter's hand is green, which corresponds to a high emissivity surface near body temperature (37 °C). The photographs also show that the white painted surface is nearly as emissive as a black surface.

A modern version of Leslie's Cube is part of the structure of a small earth-orbiting satellite known as FUNcube-1 and registered as a Dutch spacecraft. Launched in November 2013, it demonstrates the absorption and emission of solar radiation in space as the satellite orbits in full sunlight, eclipse and rotates around its three axes.

References

* In 1856, Draper described the device as a cubical brass vessel set upon a vertical rotatable stem. At a little distance is the blackened bulb of a differential thermometer. A mirror reflects the infrared rays of the cube onto the bulb. One of the sides of the cube is left with a clear surface, another with a coat of varnish, the third with two, and the fourth with three coats. It was found that more heat escaped as the number of coats increased. In the experiments of

Macedonio Melloni Macedonio Melloni (11 April 1798 – 11 August 1854) was an Italian physicist, notable for demonstrating that radiant heat has similar physical properties to those of light. Life Born at Parma, in 1824 he was appointed professor at the local Uni ...

, it was found that the maximum rate of radiation was at 16 coats. * * * *{{cite book , author = Poynting, John Henry , author2=Thomson, Joseph John , title = A Textbook of Physics , date = 1906 , publisher = Charles Griffin and Company , location = London , url = https://archive.org/details/bub_gb_RTNMAAAAMAAJ , quote = leslie cube. , pages
230
ndash;231 Radiometry 1804 introductions 1804 in science 1804 in Scotland Cubes

Device

See also

References

Further reading