The radius of the second Bohr orbit for hydrogen atom is :(Planck’s Const.h= $6.6262 \times 10^{-34}\;Js$ mass of electron $= =9.1091 \times 10^{−31}\; kg;$
charge of electron $e= 1.60210 \times 10^{-19}\;C$ permittivity of vacuum$\in_0 =8.854185 \times 10^{-12} \;kg^{-1} m ^{-3} A^2)$
