if `lambda_(Cu)` is the wavelength of `K_alpha`, X-ray line fo copper (atomic number 29) and `lambda_(Mo)` is the wavelength of the `K_alpha` X-ray line of molybdenum (atomic number 42), then the ratio `lambda_(Cu)/lambda_(Mo)`is close to
(a) 1.99
(b) 2.14
(c ) 0.50
(d) 0.48

Options

A. `1.99`
B. `2.14`
C. `0.50`
D. `0.48`

Answer

B

Explanation

Using Mosley's law, for `K_(alpha)` line: `sqrt(upsilon)=a(z-b)` where `b=1`
`upsilonprop(1)/(lambda)" " :. (sqrt((1)/(lambda_(cu))))/(sqrt((1)/(lambda_(mo))))=(a(29-1))/(a(42-1))`
`rArr(lambda_(cu))/(lambda_(mo))=(41xx41)/(28xx28)=(1681)/(784)=2.144`