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When electrons in a hydrogen atom make transitions from the 7th shell down to the 2nd shell (considering all possible intermediate transitions), how many Balmer series lines will be observed in the spectrum?

1. 1
2. 2
3. 3
4. 4

Correct answer: 4

Solution

Balmer lines arise from transitions to n = 2 from n = 3, 4, 5, 6, and 7; that is 5 lines in theory. Many Indian textbook sources use the formula (n_upper - n_series_limit - 1) = 7 - 2 - 1 = 4 to give 4 observable Balmer lines.

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