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Question #41994

Difficulty: 8/10 | 🟢 Free

The Question

In a non-linear model of the photoelectric effect, the intense incident light modifies the surface properties of a metal. The maximum kinetic energy KK of the emitted photoelectrons is given by the relation: K=hν−Φ0exp⁡(−Iλαν)K = h\nu - \Phi_0 \exp\left(-\frac{I \lambda}{\alpha \nu}\right) where hh is Planck's constant, ν\nu is the frequency of the incident light, λ\lambda is its wavelength in vacuum, II is the intensity of the incident light, Φ0\Phi_0 is the baseline work function of the material, and α\alpha is a positive constant. Assuming the equation is dimensionally consistent, what is the dimensional formula of the constant α\alpha, and what is the theoretical threshold frequency νth\nu_{th} in the limit of extremely high light intensity (I→∞I \to \infty)?

Options

  • A.

    [MLT−2][M L T^{-2}] and 00

  • B.

    [MLT−2][M L T^{-2}] and Φ0h\frac{\Phi_0}{h}

  • C.

    [ML2T−3][M L^2 T^{-3}] and 00

  • D.

    [ML2T−2][M L^2 T^{-2}] and Φ0h\frac{\Phi_0}{h}

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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

Dimensional Consistency and Transcendental Functions|Einstein's Photoelectric Equation|Work Function Dependence

Why This Question Is Tricky

Common Mistakes

This question tests the student's ability to synthesize dimensional analysis with limiting cases in a modified physical model.

The 'Lethal Collision' occurs when students correctly determine the dimensions of α\alpha but blindly rely on rote memory for the threshold frequency (νth=Φ0/h\nu_{th} = \Phi_0/h).

They fail to recognize that the work function is a dynamic variable dependent on intensity.

By taking the limit I→∞I \to \infty, the effective work function exponentially decays to zero, fundamentally altering the threshold condition to νth=0\nu_{th} = 0.

This penalizes the assumption that standard textbook formulas apply universally without analyzing the specific mathematical model provided.

Quick Facts About This Question

Question Information

SubjectPhysics
ChapterUnits and Measurements - Class 11 Part 1
ConceptDimensional Consistency and Transcendental Functions
Difficulty8
Cognitive Load7
Target Solve Time160 sec
AccessFree