Radiation of wavelength 340 nm illuminates a lithium surface with work function 2.4 eV. Calculate the photon energy in eV and the maximum kinetic energy of emitted electrons in eV. Use h = 6.626 × 10⁻³⁴ J s, c = 3.00 × 10⁸ m/s and e = 1.602 × 10⁻¹⁹ C.

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3.649 eV; 1.249 eV Photon energy E = hc/λ = (6.626 × 10⁻³⁴ × 3.00 × 10⁸) ÷ (3.4 × 10⁻⁷) = 5.85 × 10⁻¹⁹ J. In electronvolts, E = 5.85 × 10⁻¹⁹ ÷ (1.602 × 10⁻¹⁹) = 3.649 eV. Einstein's equation gives Kₘₐₓ = E − φ. Kₘₐₓ = 3.649 − 2.4 = 1.249 eV.

Photoelectric emission from lithium

Radiation of wavelength 340 nm illuminates a lithium surface with work function 2.4 eV. Calculate the photon energy in eV and the maximum kinetic energy of emitted electrons in eV. Use h = 6.626 × 10⁻³⁴ J s, c = 3.00 × 10⁸ m/s and e = 1.602 × 10⁻¹⁹ C.

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