NEET Physics EM Waves NEET PYQ-EM Waves

  • question_answer
    The energy of the EM waves is of the order of \[15\text{ }keV\]. To which part of the spectrum does it belong?                                                                                                                                                   [NEET (Re) 2015]

    A)  X-rays             

    B)   Infrared rays

    C)  Ultravioiet rays   

    D)    \[\gamma \]-rays

    Correct Answer: A

    Solution :

    Given, energy of EM waves is of the order of i.e.          
    \[E=hv=h\times \frac{c}{\lambda }\]
    \[\Rightarrow \]   \[\lambda =\frac{h\times c}{E}=\frac{6.624\times {{10}^{-34}}\times 3\times {{10}^{18}}}{15\times {{10}^{3}}\times 1.6\times {{10}^{-19}}}\]
    \[=\frac{1.3248\times {{10}^{-29}}}{1.6\times {{10}^{-19}}}={{0.82810}^{-10}}m\]
    \[=0.828\overset{{}^\circ }{\mathop{\text{A}}}\,\]         \[[1\overset{{}^\circ }{\mathop{A}}\,={{10}^{-10}}m]\]
    \[\lambda =0.828\overset{{}^\circ }{\mathop{A}}\,\]
    Thus, this spectrum is a part of X-rays.

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