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Crookes Radiometer

Crookes Radiometer

Crookes Radiometer

Original price was: KSh 1,600.00.Current price is: KSh 1,028.00.

In stock

Original price was: KSh 1,600.00.Current price is: KSh 1,028.00.

  • Light Sensitivity: The radiometer is highly sensitive to light. When exposed to light, it demonstrates a unique phenomenon where the vanes within the sealed glass chamber begin to rotate.
  • Partial Vacuum Chamber: The radiometer consists of a sealed glass chamber with a partial vacuum inside.
  • Four Vanes: Inside the glass chamber, there are typically four thin, lightweight vanes mounted on a central axis.
  • Thermal Effect: The rotation of the vanes is caused by a thermal effect resulting from the absorption and reflection of light.
  • Demonstration of Radiant Energy: The Crookes radiometer serves as a visual demonstration of radiant energy, showing the conversion of light energy into mechanical motion.

Description

Crookes Radiometer

Crookes radiometer, also known as a light mill, is a fascinating scientific device that demonstrates the conversion of light energy into mechanical motion. Invented by English physicist William Crookes in the 1870s, it remains a popular science experiment and conversation starter due to its counterintuitive nature.

Design and Functionality:

  • Glass bulb: An evacuated glass bulb creates a partial vacuum inside. This near-vacuum is crucial for the radiometer’s function.
  • Vanes: Inside the bulb, a lightweight rotor with several thin vanes (typically four) is suspended on a low-friction spindle. The vanes are often black on one side and white or polished on the other.
  • Radiation source: When exposed to light or other forms of radiant energy (like infrared radiation), the vanes begin to rotate. Sunlight, artificial light, or even the heat from a nearby hand can provide enough energy for movement.

The Science Behind the Spin:

The rotation of the vanes is a result of a phenomenon called thermal transpiration. Although initially thought to be light pressure directly pushing the vanes, the explanation lies in the behavior of gas molecules within the bulb.

  • Uneven heating: Light radiation is absorbed more readily by the black vanes compared to the white ones. This uneven heating causes the gas molecules near the black vanes to move faster.
  • Molecular collisions: The faster-moving gas molecules near the black vanes collide more frequently with the vanes themselves, transferring some of their momentum.
  • Torque generation: The unequal force from these collisions creates a net torque on the rotor, causing it to spin in the direction where the black vanes push away from the light source.

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