Calculate the wavelength of the first line in the Balmer series of hydrogen spectrum.
656.5 nm
From line spectrum of hydrogen, we know that
¯ν=RH[1n21−1n22]
=109677[1(2)2−1(3)2]cm−1
=109677×536cm−1
=1523.9cm−1
Or λ=1¯ν=115,232.9cm=6.565×10−1cm=656.5nm