NEET Sample Paper NEET Sample Test Paper-22

  • question_answer
    A potential difference of 1000 V is applied across an X - ray tube. The ratio of the de-Broglie wavelength of the incident electrons to the shortest wavelength of X - rays produced is (Take\[\frac{e}{m}=1.8\times {{10}^{14}}C/kg\]) for an electron.

    A) \[\frac{1}{20}\]                      

    B)      \[\frac{1}{100}\]                    

    C)  1                    

    D)       \[\frac{1}{{{10}^{4}}}\]

    Correct Answer: C

    Solution :

    For incident electron \[{{\lambda }_{1}}=\frac{h}{p}=\frac{h}{\sqrt{2km}}=\frac{h}{\sqrt{2\,m\,Ve}}\] and shortest wavelength of \[x\]rays is \[{{\lambda }_{2}}=\frac{hc}{eV}\] \[\therefore \]\[\frac{{{\lambda }_{1}}}{{{\lambda }_{2}}}=\frac{1}{c}\sqrt{\frac{V}{2}.\frac{e}{m}}=\frac{1}{3\times {{10}^{8}}}\sqrt{\frac{1000\times 1.8\times {{10}^{14}}}{2}}=1\] Hence, the correction option is [c].


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