Characteristic X-rays of frequency `4.2xx10^18` Hz are produced when transitions from L-shell to K-shell take place in a cartain target meterial. Use Mosley's law to determine the atoic number of the target matderial. Given Rydberg constant `R =1.1xx10^7 m^(-1)`.

Answer

B, D

Explanation

`DeltaE = hv = Rhc (Z-b)^2 ((1)/(n_1^2)- (1)/(n_2^2))`
For K-series, b-1
`:. V=Rc(Z-1)^2 ((1)/(n_1^2)- (1)/(n_2^2))`
Substituting the values,
`4.2xx10^18 = (1.1xx10^7)(3xx10^8)(Z-1)^2((1)/(1) - (1)/(4))`
`:. (Z-1)^2 = 1697`
or `Z-1 ~~ 41`
or Z = 42