The first member of the Balmer series of hydrogen atom has a wavelength of 6561 A0. The wavelength of the second member of the Balmer series (in nm) is ----

Wavelength during transition can be given as,​1λ=RZ21n12−1n22For first member of Balmer Series of Hydrogen : 1λ1=R12122−132For second member of Balmer Series of Hydrogen : 1λ2=R12122−142=3R16∴ λ2λ1=163R365R=2027​⇒λ2=2027×6561A0=4860A0 =486nm