Radiomètre sur pied
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Radiometer on stand

Radiometer on stand
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Blown glass from Lauscha (Germany)
Height: 23 cm
Diameter of the bulb: 8 cm
Beech wooden stand

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. 7501] [$, £, CHF...]

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Our customers' reviews

Average rating : 4.5/5 (11 reviews)
  5/5 , 01/02/2022
It is lovely! The radiometer is very sensitive, and the wood base is turned and finished beautifully. I'm proud to have this in my house.
  5/5 , 29/12/2021
  5/5 , 14/03/2021
  5/5 , 06/03/2020
  5/5 , 15/09/2018
Bel objet qui fonctionne très bien. La finition des palettes noires pourrait être améliorée.
, 25/11/2017
@marine Nos radiomètres sont des objets artisanaux. Cela explique les petites imperfections, qui font partie du charme de l'objet !
  2/5 , 25/11/2017
la finition des ailettes en mika est vraiment pas terrible .... et le pied est trés léger, bien + que ce que j'imaginais. Cela en fait un objet trés très fragile .
  5/5 , 11/04/2016
  4/5 , 18/11/2015
  5/5 , 03/07/2013
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