- Sections
- A. General Materials & Mathematics
- B. Statics
- C. Kinematics & Dynamics
- D. Rotational Mechanics
- E. Gravitation & Astronomy
- F. Fluid Mechanics
- G. Vibrations & Mechanical Waves
- H. Sound
- I. Thermodynamics
- J. Electrostatics & Magnetostatics
- K. Electromagnetic Principles
- L. Geometrical Optics
- M. Wave Optics
- N. Spectra & Color
- O. Vision
- P. Modern Physics
I2-01. Crookes' Radiometer
Purpose
To stimulate discussion about radiative heat transfer and conservation of momentum with photons.
Equipment
Crookes' radiometer with matches.
Images
Description
A match or other source of light is brought near the radiometer, resulting in rotation of the vanes. Two possible explanations for this include: (1) Photons are mostly absorbed by the black side of each vane, but are mostly reflected by the white side, thus transferring more momentum to the white side, producing rotation in the direction of the black side with the white side trailing. (2) Photons are mostly absorbed by the black side, but mostly reflected by the white side, thus heating the black side more.Air molecules coming into contact with the vanes will obtain more heat energy from the
References
Gordon F. Hull, Concerning the Action of the Crookes Radiometer, AJP 16, 185-186, (1948). H. V. Neher, Light-Pressure Tube, AJP 29, 666-668 (1961)
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See pagesi1. thermal properties of matter
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See pagesi2. transfer of heat
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See pagesi3. gases
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See pagesi4. changes of state
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See pagesi5. laws of thermodynamics
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See pagesi1. thermal properties of matter
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See pagesi2. transfer of heat
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See pagesi3. gases
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See pagesi4. changes of state
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See pagesi5. laws of thermodynamics
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