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Wilson Cloud Chamber (Principle, Construction & Working)

Wilson is 1911, invented a cloud chamber (called Wilson cloud chamber) to detect the presence of radioactive particles. To identify them and to measure their energy. Let us discuss the complete setup of Wilson cloud chamber.


If we suddenly increase the volume of air saturated with water vapor, the temperature of air falls sharply and it becomes supersaturated with water vapor.

The vapor is condensed in the form of small droplets on the dust particles, present in the air and a fog appears.
If there be no dust particle in the air the vapor will not be condensed and the fog will not appear. If however we ionizing duet free air by some ionizing radiation ( like α, β particle ).
Then the vapor is condensed on the ions produced in the air. Thus by seen condensation of water vapor in the dust-free air. The presence of α and the β particle can be detected.

Construction of Wilson Cloud Chamber

Wilson’s cloud chamber consists of a cylindrical metallic chamber C fitted with glass top G and carrying a movable piston P, the space between piston P and glass cover filled with dust free air saturated with water vapor intense light is sent into the chamber through a window. Just above the chamber, a camera is fitted.

Wilson Cloud Chamber

The α or β particle emitted by the radioactive substance enter the chamber. Each particle goes on producing ion by ionizing the air molecules on its path. To mark the path of the particle the piston P is dropped down which leads to  a sudden expansion  of the saturated air in the chamber. Hence the air is called and  becomesuper saturated with water vapour. Now the vapour condensed in the form of drops of ions formed along the path of the particle.
Thre path of the particle is marked as a trail of the droplet which is the track of the particle . it is photographed of the camera. The process ids automatic as soon as the particle enters the chamber, the position drops down the shutter of the camera opens & track of particle is photographed by the camera.
This is how Wilson Cloud Chamber works. You can always ask your queries in the comment section.
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