Laws of Photoelectric Emission
1. Instantaneous emission (no time lag). 2. Rate of photoelectron emission ∝ light intensity. 3. Maximum KE depends strictly on frequency ν, independent of intensity. 4. No emission below threshold frequency ν₀.
Grade 12th · Physics · Dual Nature of Radiation and Matter
Dual Nature of Radiation: Einstein's Photoelectric Equation
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Science StreamAdvanced Level
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Essential Formulas & Mathematical Definitions
Kmax = h ν - Φ₀ = e V₀
Work Function: Φ₀ = h ν₀
de Broglie: λ = h / √(2m e V) ≈ 1.227 / √V nm (for electron)
Stopping Potential (V₀)
The negative anode potential required to stop the fastest emitted photoelectrons: eV₀ = Kmax = hν - Φ₀.
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Exam Day Revision & Problem Solving Checklist
- ✓Slope of Stopping Potential V₀ vs Frequency ν graph equals (h / e)
- ✓X-intercept of V₀ vs ν graph represents threshold frequency ν₀
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High-Yield Exam Strategy & Scoring Tips
Step-by-Step Mark Allocation
Always state the governing principle or formula first, write given values with standard SI units, substitute clearly, and highlight the final numerical answer with units in a box for full step marking.
Common Calculation Traps
Watch for unit prefixes (cm to m, minutes to seconds, g to kg, degrees to radians). In coordinate and ray optics problems, double-check Cartesian sign conventions before computing.
Recommended Practice & Calculation Tools
Test your understanding and perform instant calculations with these free online utilities.
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Frequently Asked Exam Questions & Concept Clarifications
Why could wave theory of light not explain the photoelectric effect?
Wave theory predicted that kinetic energy would depend on intensity and that there would be a time lag for energy accumulation, contradicting experimental facts.