A copy-ready table of the constants chemistry numericals use: Avogadro, both values of R, Planck, the speed of light, the elementary charge, Boltzmann, Faraday, electron and proton mass, standard pressure, molar volume, Rydberg and ε₀. Tap a value to copy it.
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From the article Scientific Constants — Which to Memorise and Why.
Derive it.
hc = (6.626 070 15 × 10⁻³⁴) × (2.997 924 58 × 10⁸) = 1.986 446 × 10⁻²⁵ J m
Convert to eV: ÷ (1.602 176 634 × 10⁻¹⁹) = 1.239 842 × 10⁻⁶ eV m
Convert metres to nanometres: × 10⁹ = 1239.84 eV nm ≈ 1240 eV nm
Use it. Energy of a 500 nm photon:
E = 1240 ÷ 500 = 2.48 eV
Cross-check the long way.
E = hc/λ = (1.986 446 × 10⁻²⁵) ÷ (500 × 10⁻⁹) = 3.9729 × 10⁻¹⁹ J
÷ (1.602 177 × 10⁻¹⁹) = 2.48 eV ✓
Worked in full in Scientific Constants — Which to Memorise and Why.
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