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In a hydrogen atom, an electron jumps from the nth shell to the ground state. If the number of spectral lines in the Paschen series is 3, what is the value of n?

1. 4
2. 5
3. 6
4. 7

Correct answer: 6

Solution

Paschen series lines arise from transitions to n=3 level. If the electron starts at nth shell, the Paschen series lines are from levels 4, 5,..., n each dropping to 3, giving (n - 3) lines. Setting n - 3 = 3 gives n = 6.

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