Solid targets of different elements are bombarded by highly energetic electron beam. The frequcny `(f)` of the characteristic `X`-rays emitted from different targets varies with atomic number `Z` as

Options

A. `f prop sqrt(Z)`
B. `f prop Z^(2)`
C. `f prop Z`
D. `f prop Z^(1//2)`

Answer

B

Explanation

According to Mosely's law
`(Z-sigma)prop sqrt(f)" or, "f prop (Z-sigma)^(2)`.
Note: The correct answer should have been `fprop (Z-sigma)^(2)` where `sigma` is the screening constant. Many authors use at this level, `sigma=1` approximately.