Wavelength of a particular transition of H atom is 400 nm. What an be the wavelength of `He^(+)` for the same transition-

Options

A. 400nm
B. 100nm
C. 1600nm
D. 200nm

Answer

B

Explanation

`(1)/(lamda)=R_(H)((1)/(n_(1)^(2))-(1)/(n_(2)^(2)))xxZ^(2)`
`(1)/(400)=R_(H)((1)/(n_(1)^(2))-(1)/(n_(2)^(2)))(1)^(2)` . . . (1)
`(1)/(lamda_(He^(+)))=R_(H)((1)/(n_(1)^(2))-(1)/(n_(2)^(2)))(2)^(2)` . . . (2)
On dividing equation (1) and (2), we get
`lamda_(He^(+))=(400)/(2^(2))=(400)/(4)=100nm`