Which of the following statements about hydrogen spectrum are correct?

Answer

A, C

Explanation

First line of Lyman series is obtained during transition of hydrogen atom from `n = 2 to n = 1`. Hence , its energy is equal to `E_(2) - E_(1) = (13.6) eV - (- 3.4 eV) = - 1.2 eV`.
`:.` Wavelength of the first line of Lyman series is equal to
`(12375)/(10.2) Å = 1215 Å`
Therefore, it line in ultraviolet region.
Since energy of all the other line of Lyman series is greater than that of first line , therefore all the lines of Lyman series lie in ultraviolet region. Hence option (a) is correct
First line of Lyman series is obtained during transition of hydrogen atom from `n = 3 to n = 2`. Hence , its energy is equal to `E_(3) - E_(2) = 1.89 eV`.
`:.` Wavelength of the first line of Balmer series is equal to
`12375//1.89 Å = 6563 Å`. It lines in visible region.
Energy of the last line of Balmer series is equal to `3.4 eV`. Therefore, its wavelength is equal to `12375//3.4 Å = 3640 Å`.
Since it is less than `4000 Å`, therefore it lines in ultraviolet region. Hence ,option (b) is wrong . Energy of the last line of Paschen series is equal to `1.51 eV`. It lines in infrared region. Since energy of alll the other lines of Paschen series is less than its energy, therefore all the lines of Paschen series will be in infrared region. Hence ,option ( c) is also correct.