 The graph above shows the intensity of X-rays vs wavelength for an X-ray tube. The cutoff wavelength $\lambda_{\min}$ shown in the diagram is determined ONLY by
Athe target material
Bthe filament temperature
Cthe accelerating voltage across the tube
Dthe number of electrons reaching the anode per second
Answer & Solution
Correct answer: C. the accelerating voltage across the tube
$\lambda_{\min} = \dfrac{hc}{eV}$ — a purely kinematic limit set by how much energy a single electron can convert to a photon. The peak $K_\alpha$ position depends on the target material, but the *cutoff* $\lambda_{\min}$ depends only on the accelerating voltage $V$.
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