Sample 1Medium
A graph of stopping potential V₀ (y-axis) against frequency ν of the incident light (x-axis) for a metal is a straight line that cuts the frequency axis at 5 × 10¹⁴ Hz. Take h = 6.63 × 10⁻³⁴ J s and 1 eV = 1.6 × 10⁻¹⁹ J. What is the work function of the metal?
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The answer is C.
The intercept is the threshold frequency ν₀, and the work function φ₀ = hν₀ = 6.63 × 10⁻³⁴ × 5 × 10¹⁴ = 3.3 × 10⁻¹⁹ J ≈ 2.07 eV.
- A.
3.3 is the value in units of 10⁻¹⁹ J, not in eV.
- B.
1.24 eV corresponds to a threshold of 3 × 10¹⁴ Hz, not 5 × 10¹⁴ Hz.
- D.
4.14 eV is twice hν₀.
NCERT: Class 12 Physics, Chapter 11