Question

An X-ray tube operates at 20 kV. A particular electron loses 5% of its kinetic energy to emit an X-ray photon at the first collision. What is the wavelength corresponding to this photon? Given that Planck's constant $=4.14\times {10}^{-15}eVs$.

• A. 1.54 nm
• B. 2.32 nm
• C. 0.68 nm
• D. 1.24 nm

Answer 1

The correct option is D

1.24 nm

Kinetic energy of the electron, $K=20\times {10}^{3}eV$
Energy of photon, $E=0.05K={10}^{3}eV$
Now, $\frac{hc}{\lambda }={10}^3\Rightarrow \lambda =\frac{4.14\times {10}^{-15}\times 3\times {10}^8}{{10}^3}=1.24nm$
Hence, the correct choice is (d).