Radiation force

These notes were inspired by discussions at the 2024 Physical Acoustics Summer School.

1. Radiation force of pendulum
• By the virial theorem
• By adiabatic invariance
2. Radiation force of a string
• As a consequence of linear equations of motion
• As a consequence of nonlinear equations of motion
3. Radiation force and torque of sound
• Energy densities
• Conservation of energy
• Conservation of momentum
• Linear momentum
• Angular momentum
• Reduction to time-averaged quantities
• Acoustic radiation force and torque
• Due to traveling waves
• Due to standing waves
• Is radiation force a linear or nonlinear effect?
• Arguments as to why radiation force is a nonlinear effect
• Arguments as to why radiation force is a linear effect
• Resolution
4. Radiation force of light
5. Example: Radiation force on rigid sphere
6. Useful identities
7. References

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