The ratio of longest wavelength corresponding to Lyman and Blamer series

The ratio of longest wavelength corresponding to Lyman and Blamer series in hydrogen spectrum is

(a) 3 / 23
(b) 7 / 29
(c) 9 / 13
(d) 5 / 27

5 / 27

For Lyman series (2 → 1)
1/λL = R [1 – 1/2] = 3R/4
For Balmer series (3 → 2)
1/λB = R [1/4 – 1/9] = 5R/36
λL / λB = 4/3R / 36/5R = 4/36 (5/3) = 5/27

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