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Question #43772
The Question
In a precision photoelectric experiment, a metallic emitter (work function ) is maintained at temperature and illuminated by monochromatic light of photon energy . Classically, the photocurrent exhibits a sharp cutoff, dropping to zero at the stopping potential . However, due to thermal energy partitioning, the initial energies of electrons inside the metal follow the Fermi-Dirac distribution , where is the energy measured relative to the Fermi level. Assuming the density of states is constant and the emission probability is uniform for all electrons energetically capable of reaching the collector against a retarding potential , the saturation curve blurs into a continuous tail. Evaluate the ratio , where .
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
Heisenberg's Limitation|Photoelectric Saturation|Energy Partitioning
Why This Question Is Tricky
Common Mistakes
This question targets the misconception that the photoelectric saturation curve has a sharp, absolute cutoff at .
Students often fail to account for the thermal energy partitioning of electrons in the metal, which follows the Fermi-Dirac distribution.
A common trap is to either assume the current is strictly zero for , or to incorrectly apply the classical Maxwell-Boltzmann approximation () near the Fermi level, which would erroneously yield a ratio of (Option B).
By forcing the evaluation of the exact Fermi-Dirac integral at the classical boundary, the problem tests the student's ability to reconcile quantum statistical mechanics with the semi-classical photoelectric equation.
Quick Facts About This Question
Question Information
| Subject | Physics |
| Chapter | Dual Nature of Radiation and Matter - Class 12 |
| Concept | Heisenberg's Limitation |
| Difficulty | 8 |
| Cognitive Load | 7 |
| Target Solve Time | 160 sec |
| Access | Free |