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12.Atoms
normal
The wavelength of ${K_\alpha }$ line for an element of atomic number $29$ is $\lambda $ . Then the wavelength of ${K_\alpha }$ line for an element of atomic no $15$ is (Take mosley‘s constant $b = 1$ for both elements)
A
$\frac{{29}}{{15}}\lambda $
B
$\frac{{28}}{{15}}\lambda $
C
$4\lambda $
D
$2\lambda $
Solution
$\frac{1}{\lambda} \propto(Z-b) 2$
$\frac{\lambda_{2}}{\lambda_{1}}=\frac{\left(Z_{1}-b\right)^{2}}{\left(Z_{2}-b\right)^{2}}=\left(\frac{28}{14}\right)^{2}=4$
$\boxed{{\lambda _2} = 4{\lambda _1}}$
Standard 12
Physics
