1
Xa+ and Yb+ are hydrogen-like species. The wavelength of light absorbed during the transition between the states with principal quantum numbers n=1 and n=2 of Xa+ is . The wavelength of light absorbed during the transition between the states with principal quantum numbers n=2 and n=4 of Yb+ is 9 . The lowest possible value of (a+b) is .
Answer
3
Solution
1 =RHZ2 ( 1n12- 1n22 )
X: 1 =RHZX2 34; Y: 19 =RHZY2 ( 14- 116 )=RHZY2 316
Dividing: 9= 4ZX2ZY2 ZXZY= 32
Smallest integers: ZX=3 ( Li2+, a=2), ZY=2 ( He+, b=1)
a+b=3
Answer: 3
JEE Advanced 2026 Paper 2