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Energy of an electron is given by E = – 2.178 × 10 –18 J ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ 2 2 n Z . Wavelength of light required to excite an electron in an hydrogen atom from level n = 1 to n = 2 will be : (h = 6.62 × 10 –34 Js and c = 3.0 × 10 8 ms –1 )

1. 6.500 × 10 –7 m
2. 8.500 × 10 –7 m
3. 1.214 × 10 –7 m
4. 2.816 × 10 –7 m

Correct answer: 1.214 × 10 –7 m

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