Question

The voltage applied to an X-ray bulb increases to 1.5 times the initial voltage. The short wavelength limit of continuous X-ray spectrum shifts by 25 pm. Then

• A. Initial voltage applied is $160\times {10}^3$kV
• B. Initial voltage applied is $80\times {10}^3$kV
• C. Initial wavelength is $75pm$
• D. Final wavelength is $150pm$

Answer 1

Answer: (C)

Initial wavelength is $75pm$

$\lambda =\frac{hc}{eV}$
${\lambda }^1=\frac{2hc}{3eV}$
$\lambda -25=\frac{2hc}{3eV}$
so, $\frac{\lambda }{\lambda -25}=\frac{3}{2}$
$2\lambda =3\lambda -75$
$\lambda =75pm$

So, the answer is option (C).