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Question #43117
The Question
An RLC circuit with resistance and inductance drives an antenna, emitting a plane electromagnetic pulse. Due to the circuit's damping, the emitted pulse is not monochromatic but has a Lorentzian energy fluence spectrum (energy per unit area per unit angular frequency) given by: where is the total energy fluence, is the central frequency, and is the spectral half-width. This pulse is normally incident on a resonant microscopic solar sail. The sail's effective absorption area depends on the frequency of the incident radiation as: where is the peak area and is the resonance half-width of the sail. Assuming the sail absorbs the radiation completely according to this profile and reflects nothing, what is the total momentum imparted to the sail? (Assume so the integration limits can be approximated as to ).
Options
- A.
- B.
- C.
- D.
Check Your Answer
Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Intuition_Breaker
Train your brain to resist "obvious" answers that are designed to deceive your intuition.
Concepts Behind This Question
Source of EM Waves|Energy Density Partitioning|Wave-Particle Duality Constraint
Why This Question Is Tricky
Common Mistakes
This question tests the boundary between idealized monochromatic waves and real-world damped oscillators.
Students commonly fall into the trap of assuming the RLC circuit emits a single frequency (ignoring the bandwidth caused by the resistor).
If they assume a monochromatic source, they evaluate the absorption area only at the peak, yielding and .
However, the Uncertainty Principle embedded in the circuit's Q-factor dictates a Lorentzian spectral spread.
Calculating the true momentum requires convolving the source's emission spectrum with the target's absorption spectrum, which significantly reduces the transferred momentum due to the spectral mismatch.
Quick Facts About This Question
Question Information
| Subject | Physics |
| Chapter | Electromagnetic Waves - Class 12 |
| Concept | Source of EM Waves |
| Difficulty | 8 |
| Cognitive Load | 7 |
| Target Solve Time | 160 sec |
| Access | Free |