Dual Nature Of Light Question 104
Question: Electrons with energy 80 keV are incident on the tungsten target of an X-ray tube. K shell electrons of tungsten have ionization energy 72.5 keV. X-rays emitted by the tube contain only [IIT-JEE (Screening) 2000]
Options:
A) A continuous X-ray spectrum (Bremsstrahlung) with a minimum wavelength of ~ 0.155Å
B) A continuous X-ray spectrum (Bremsstrahlung] with all wavelengths
C) The characteristic X-rays spectrum of tungsten
D) A continuous X-ray spectrum (Bremsstrahlung) with a minimum wavelength of ~ 0.155Å and the characteristic X-ray spectrum of tungsten
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Answer:
Correct Answer: D
Solution:
Minimum wavelength of continuous X-ray spectrum is given by $ {\lambda_{\min }}(in {\AA})=\frac{12375}{E(eV)}=\frac{12375}{80\times 10^{3}}\approx 0.155 $ Also the energy of the incident electrons (80 KeV) is more than the ionization energy of the K-shell electrons (i.e. 72.5 KeV). Therefore characteristic X-ray spectrum will also be obtained because energy of incident electron is enough to knock out the electron from K or L shells.
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