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

Answer

B, D

Explanation

Transition if from L-shell ot K-shell.
`(1)/(lambda)= R (Z-1)^2 ((1)/(n_1^2) - (1)/(n_2^2))`
or `(f)/(c ) = R(Z-1)^2 ((1)/(n_1^2) - (1)/(n_2^2))`
or `(4.2xx10^8)/(3xx10^8) = 1.1 xx10^7 (Z -1)^2((1-(1)/(4))`
Solving we get, Z = 42.