The transition from the state n = 4 to n =3 in a hydrogen like atom results in ultraviolet radiation. Infrared radiation will be obtained in the transition from :

1λα1n12−1n22;∴1λuvα132−142 ∴λuv∝20.5According to options :1. 1λ1∝122-132∴λ1∝7.22. 1λ2∝122-142∴λ2∝5.33. 1λ3∝142-152∴λ3∝44.44. 1λ4∝112-122∴λ4∝1.3For IR radiation :λIR>λuv ; i.e., λ3 > λuvSo, transition should take place from 5 → 4