Ultraviolet lies in Lymen series. Long corresponds to minimum energy which ocd from n=2 to n=1.λ1​Zλ122​=RZ2(nf2​1​−ni2​1​)=1=R(nf2​1​−ni2​1​)1​=(121​−221​)R1​​…(i)​The smallest wavelength in the infrared region corresponds to maximum energy of Paschen series.λ=(321​−∞1​)R1​​…(ii)Solving Eqs. (i) and (ii), we getλ=823.5 nm