The wavelength of `K_(alpha)` X-rays of two metals `A and B` are` 4 // 1875 R and 1// 675 R`, respectively , where `R` is rydberg 's constant. The number of electron lying between `A and B` according to this lineis

Options

A. 3
B. 6
C. 5
D. 4

Answer

D

Explanation

Using `(1)/(lambda) = R (Z - 1)^(2) [(1)/(n_(2)^(2)) - (1)/(n_(1)^(2))]`
For `K_(alpha)` line, `n_(1) = 2, n_(2) = 1`
For matel `A: (1875 R)/(4) = R (z - 1)^(2)((3)/(4))`
`implies z_(1) = 31`
Therefore , `4` element lie between `A and B`.