A doubly ionized lithium atom is hydrogen like with atomic number 3. Find the wavelength of the radiation required to excite the electron in `Li^(++)` from the first to the third Bohr orbit (ionization energy of the hydrogen atom equals 13.6 eV).

Explanation

Given for `Li^(+ +)` Z=3 and as the excitation is from first to third Bohr orbit, so `n_(1)=1,n_(2)=3`
Using the realation
`(1)/(lambda)=Z^(2)R((1)/(n_(1)^(2))-(1)/(n_(2)^(2)))=(3)^(2)R((1)/(1^(2))-(1)/(3^(3)))=8R`
`rArr` Wanelength `lambda=(1)/(8R)=(1)/(8xx1.097xx10^(7))=0.114xx10^(-7)`
`=11.4 nm`