Hydrogen $(H)$, deuterium $(D)$, singly ionized helium $(H{e^ + })$ and doubly ionized lithium $(Li)$ all have one electron around the nucleus. Consider $n =2$ to $n = 1 $ transition. The wavelengths of emitted radiations are ${\lambda _1},\;{\lambda _2},\;{\lambda _3}$ and ${\lambda _4}$ respectively. Then approximately

• A

  ${\lambda _1} = {\lambda _2} = 4{\lambda _3} = 9{\lambda _4}$

• B

  $4{\lambda _1} = 2{\lambda _2} = 2{\lambda _3} = {\lambda _4}$

• C

  ${\lambda _1} = 2{\lambda _2} = 2\sqrt 2 {\lambda _3} = 3\sqrt 2 {\lambda _4}$

• D

  ${\lambda _1} = {\lambda _2} = 2{\lambda _3} = 3\sqrt 2 {\lambda _4}$