What is the threshold wavelength for a metal whose work function is 2.0 eV (h = 6.63 × 10⁻³⁴ J s, c = 3.0 × 10⁸ m/s, e = 1.6 × 10⁻¹⁹ C)?
Correct answer C. 622 nm
Explanation
λ₀ = hc/φ = 1.989 × 10⁻²⁵/(2.0 × 1.6 × 10⁻¹⁹) = 1.989 × 10⁻²⁵/3.2 × 10⁻¹⁹ = 6.22 × 10⁻⁷ m = 622 nm.
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