The wavelength of `K_(alpha)` line for an element of atomic number `43 is lambda`. Then the wavelength of `K_(alpha)` line for an element of atomic number `29` is

Options

A. `(43//29) lambda`
B. `(42//28) lambda`
C. `(9//4) lambda`
D. `(4//9) lambda`

Answer

C

Explanation

`1/(lambda) = R(Z - 1)^(2) [(1)/(n_(1)^(2)) - (1)/(n_(2)^(2))]`
For `K_(alpha)` line, `n_(1) = 1, n_(2) = 2`
`1/(lambda) = R(43-1)^(2) [(1)/(1^(2)) - (1)/(2^(2))] = R(42)^(2)(3/4)"……"(i)`
and `(1)/(lambda') = R(29-1)^(2)[(1)/(1^(2)) - 1/(2^(2))] = R(28)^(2)(3/4)"......."(ii)`
Divinding eq. (i) by (ii). we get `(lambda')/(lambda) = 9/4 rArr lambda' = 9/4lambda`