Question

Wave number of spectral line for a given transition is `x cm^(-1)` for `He^(+)`, then its value for `Be^(3+)` (isoelectronic of `He^(+))` for same transition is:
A. (a)`x cm^(-1)`
B. (b)`4x cm^(-1)`
C. (c )`x/4 cm^(-1)`
D. (d)`2x cm^(-1)`

Answer 1

Correct Answer - B
`bar(upsilon)` wave number `= bar(R)_(H)Z^(2)[1/n_(1)^(2)-1/n_(2)^(2)]`
`bar(upsilon) prop z^(2)` if `n_(1)` and `n_(2)` are same
`bar(upsilon)_(1)/bar(upsilon)_(2)=z_(2)^(1)/z_(2)^(2)implies x/bar(upsilon)_(2)=2^(2)/4^(2)`
`x/bar(upsilon)_(2)=4/(4xx4)implies upsilon_(2)=4x`