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. 1
C. 4
D. 5

Answer

C

Explanation

Using `(1)/( lamda) = R (Z-1) ^2 [(1)/( n_(2)^(2) ) - (1)/( n_(1)^(2))]`
for ` alpha ` particle ,`n_1 =2 ,n_2 =1`
for metal `A : ( 1875 R )/( 4 ) = R (Z_1 -1)^2 (3/4) implies Z_1 =26`
for mental B: `675 R =R (Z_2 -1)^2 (3/4 ) implies Z_2 =31`
therefore ,4 elements lie between A and B = 220 meV.