Easy MCQ +4 / -1 PYQ · JEE Mains 2021

What should be the order of arrangement of de-Broglie wavelength of electron ($\lambda$e), an $\alpha$-particle ($\lambda$a) and proton ($\lambda$p) given that all have the same kinetic energy?

  1. A $\lambda$<sub>e</sub> = $\lambda$<sub>p</sub> = $\lambda$<sub>$\alpha$</sub>
  2. B $\lambda$<sub>e</sub> &lt; $\lambda$<sub>p</sub> &lt; $\lambda$<sub>$\alpha$</sub>
  3. C $\lambda$<sub>e</sub> &gt; $\lambda$<sub>p</sub> &gt; $\lambda$<sub>$\alpha$</sub> Correct answer
  4. D $\lambda$<sub>e</sub> = $\lambda$<sub>p</sub> &gt; $\lambda$<sub>$\alpha$</sub>

Solution

$\lambda = {h \over p} = {h \over {\sqrt {2mE} }} \propto {1 \over {\sqrt m }}$<br><br>m<sub>$\alpha$</sub> &gt; m<sub>p</sub> &gt; m<sub>e</sub><br><br>So, $\lambda$<sub>e</sub> &gt; $\lambda$<sub>p</sub> &gt; $\lambda$<sub>$\alpha$</sub>

About this question

Subject: Physics · Chapter: Dual Nature of Matter and Radiation · Topic: Photoelectric Effect

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