Radiomètre en lune

Moon Radiometer

Moon Radiometer
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Blown glass from Lauscha (Germany)
Height : 19 cm
Diameter of the bulb: 8 cm
Wooden stand
Color : natural wood

How does it work?

A Crookes' radiometer has four vanes suspended inside a glass bulb. Inside the bulb, there is a good vacuum. When you shine a light on the vanes in the radiometer, they spin -- in bright sunlight, they can spin at several thousand rotations per minute!
The vacuum is important to the radiometer's success. If there is no vacuum (that is, if the bulb is full of air), the vanes do not spin because there is too much drag. If there is a near-perfect vacuum, the vanes do not spin unless they are held in a frictionless way. If the vanes have a frictionless support and the vacuum is complete, then photons bouncing off the silver side of the vanes push the vanes, causing them to rotate. However, this force is exceedingly small.

If there is a good but incomplete vacuum, then a different effect called thermal transpiration occurs along the edges of the vanes. The effect looks as though the light is pushing against the black faces. The black side of the vane moves away from the light.

[Ref. 7504] [$, £, CHF...]

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Our customers' reviews

Average rating : 4.67/5 (9 reviews)
  5/5 , 30/05/2018
  5/5 , 20/12/2017
Petit objet (je le voyais un peu plus grand, mais je ne suis pas déçue.) très séduisant. J'adore. Le support en bois est très joli. J'espère que la personne à qui je vais l'offrir à Noël l'aimera autant que moi.
  5/5 , 15/12/2017
Parfait (juste un détail: bien vérifier les dimensions, car l'objet parait plus impressionnant sur la photo du site!)
  5/5 , 13/01/2017
+++
  5/5 , 25/11/2016
  5/5 , 06/12/2013
  4/5 , 07/06/2013
  4/5 , 18/12/2012
Très joli en décoration et tourne avec la lumière de la fenêtre. Toutefois les pâles semblent assez fragiles et leur fixation n'est pas trop esthètique.
  4/5 , 18/12/2012
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