ArticleslgStudy

science

Leslie cube

Leslie cube is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Leslie cube rather than just read about it. In short: A Leslie cube, or Leslie's cube, is a device used in the measurement or demonstration of the variations in thermal radiation emitted from different surfaces at the same temperature. It is composed of a cube filled with water with different coatings in each surfaces.

Leslie cube — main illustration
Leslie cube — illustration

Key takeaways

  • Leslie cube belongs to science; place it in that map before memorising details.
  • Learn the definition first, then one example that makes the definition concrete.
  • Connect Leslie cube to a quantity you can measure, compute or draw — that is where exam questions come from.
  • Reproduce the core statement of Leslie cube from memory before moving on to harder problems.

Reference excerpt

A Leslie cube, or Leslie's cube, is a device used in the measurement or demonstration of the variations in thermal radiation emitted from different surfaces at the same temperature. It is composed of a cube filled with water with different coatings in each surfaces. It demonstrated the different emissivities of different materials.

Device

The cube The Leslie cube 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, and the fourth with a varnish of isinglass. The cube is made from a solid block of metal with a central cavity. In use, the cavity is filled with hot water; the entire cube has essentially the same temperature as the water.

Mirror and detector Leslie added a concave mirror next to the cube to focus radiant heat into a thermometer. He used a differential thermometer consisting of a U-shaped capillary tube, with one arm having a very narrow and the other a wider. At each end of the tube were identical sealed glass bulbs filled with air, forming a closed system. The capillaries were filled with sulfuric acid tinted with carmine. When one bulb received more radiant heat than the other, the liquid column in the capillary moved, with the displacement reflecting the temperature difference between the two bulbs. To measure radiant heat, the instrument was placed so that one bulb was located at the focal point of a concave mirror.

Modern explanation In contemporary terms, the emissivities of shiny metals are low. Isinglass is an organic glue and has a much greater 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.

Legacy

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 and eclipse and rotates around its three axes.

See also Blackbody radiation Emissivity

References

Further reading Draper, John William (1861). Textbook on chemistry. New York: Harper and Brothers. p. 68. draper, john william. 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, it was found that the maximum rate of radiation was at 16 coats. Leslie, John (1804). An Experimental Inquiry into the Nature and Propagation of Heat. Edinburgh: J. Mawman. John Leslie. Leslie, John (1813). A Short Account of Experiments and Instruments, Depending on the Relations of Air to Heat and Moisture. Edinburgh: William Blackwood. john leslie mathematics. Olson, Richard (September 1969). "A Note on Leslie's Cube in the Study of Radiant Heat". Annals of Science. 25 (3): 203–208. doi:10.1080/00033796900200111. Poynting, John Henry; Thomson, Joseph John (1906). A Textbook of Physics. London: Charles Griffin and Company. pp. 230–231. leslie cube.

Illustrations

Leslie cube: A Leslie cube (left) and a thermal detector (right)
A Leslie cube (left) and a thermal detector (right)
Leslie cube: Draper's 1861 description of the Leslie cube
Draper's 1861 description of the Leslie cube
Leslie cube: The upper images of Leslie's cube (in color) are thermographs generated by an infrared camera; the black and white images underneath are photographs taken with an ordinary camera. The face of the cube that has been painted black emits thermal radiation strongly. The polished face of the aluminum cube emits much more weakly, and the reflected image of the warm hand is clear.
The upper images of Leslie's cube (in color) are thermographs generated by an infrared camera; the black and white images underneath are photographs taken with an ordinary camera. The face of the cube that has been painted black emits thermal radiation strongly. The polished face of the aluminum cube emits much more weakly, and the reflected image of the warm hand is clear.
Leslie cube: FUNcube-1 in the cleanroom before launch
FUNcube-1 in the cleanroom before launch

Worked examples

Example 1 — a first encounter with Leslie cube

Start with the simplest possible case. Write down what Leslie cube claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Leslie cube before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Leslie cube ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Leslie cube

In research
Leslie cube appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry
Engineering practice reuses Leslie cube in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom
Leslie cube is common in secondary-school and first-year university syllabi. It links to neighbouring topics 1804 in Scotland, 1804 in science, 1804 introductions, so understanding it makes those chapters shorter.
In everyday life
Look for Leslie cube outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study Leslie cube in 20 minutes

  1. Read the reference excerpt below once, without taking notes.
  2. Close the page and write down what Leslie cube means in your own words.
  3. Compare your version with the excerpt and mark what you missed.
  4. Work through the three examples above with pen and paper.
  5. Explain Leslie cube out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Leslie cube in simple terms?

A Leslie cube, or Leslie's cube, is a device used in the measurement or demonstration of the variations in thermal radiation emitted from different surfaces at the same temperature. It is composed of a cube filled with water with different coatings in each surfaces.

Why does Leslie cube matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Leslie cube?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Leslie cube.

Tags

  • 1804 in Scotland
  • 1804 in science
  • 1804 introductions
  • Cubes
  • Radiometry

Keep exploring