NEET Sample Paper NEET Sample Test Paper-15

  • question_answer When a beam of accelerated electrons hits a target a continuous X-ray spectrum is emitted from the target. Which one of the following wavelength is absent in the X-ray spectrum if the X-ray tube is operating at 40,000 volt?

    A) \[1.5\overset{\text{o}}{\mathop{\text{A}}}\,\]                     

    B) \[~0.5\text{ }\overset{\text{o}}{\mathop{\text{A}}}\,\]

    C) \[0.25\overset{\text{o}}{\mathop{\text{A}}}\,\]                   

    D) \[1.0\overset{\text{o}}{\mathop{\text{A}}}\,\]

    Correct Answer: C

    Solution :

    Cut off wave length \[={{\lambda }_{\min }}=\frac{hc}{eV}=\frac{12375}{40000}\overset{\text{o}}{\mathop{\text{A}}}\,=0.31\overset{\text{o}}{\mathop{\text{A}}}\,\] Hence, wavelength of \[0.25\text{ }\overset{\text{o}}{\mathop{\text{A}}}\,\]must be absent in the X-rays given out by the tube. Hence, the correction option is [c].

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