Radiation of wavelength 280 nm illuminates a sodium surface with work function 1.8 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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4.432 eV; 2.632 eV Photon energy E = hc/λ = (6.626 × 10⁻³⁴ × 3.00 × 10⁸) ÷ (2.8 × 10⁻⁷) = 7.1 × 10⁻¹⁹ J. In electronvolts, E = 7.1 × 10⁻¹⁹ ÷ (1.602 × 10⁻¹⁹) = 4.432 eV. Einstein's equation gives Kₘₐₓ = E − φ. Kₘₐₓ = 4.432 − 1.8 = 2.632 eV.

Photoelectric emission from sodium

Radiation of wavelength 280 nm illuminates a sodium surface with work function 1.8 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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