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The energy of an electron is expressed as E = -2.178 × 10⁻¹⁸ (Z² / n²). For a hydrogen atom, the wavelength of radiation needed to promote an electron from n = 1 to n = 2 is (take h = 6.62 × 10⁻³⁴ Js and c = 3.0 × 10⁸ m/s):
- 1.214 × 10⁻⁷ m
- 2.816 × 10⁻⁷ m
- 6.500 × 10⁻⁷ m
- 8.500 × 10⁻⁷ m
Correct answer: 1.214 × 10⁻⁷ m
Solution
DeltaE(1->2) = 2.178e-18 x 0.75 = 1.6335e-18 J; lambda = (6.62e-34 x 3e8)/1.6335e-18 = 1.214e-7 m. The stored 2.816e-7 m is wrong.
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