Q.
The shortest wavelength of the Brackett series of hydrogen like atom (atomic number =Z) is the same as the shortest wavelength of the Balmer series of hydrogen atom. The value of Z is
Shortest wavelength of Brackett series corresponds to the transition of electron between n1=4 and n2=∞ and the shortest wavelength of Balmer series corresponds to the transition of electron between n1=2 and n2=∞
So, Z2(4213.6)=2213.6
or Z2(1613.6)=413.6
or Z2=4
or Z=2