Medium MCQ +4 / -1 PYQ · JEE Mains 2021

An $\alpha$ particle and a proton are accelerated from rest by a potential difference of 200V. After this, their de Broglie wavelengths are $\lambda$$\alpha$ and $\lambda$p respectively. The ratio ${{{{\lambda _p}} \over {{\lambda _\alpha }}}}$ is :

  1. A 8
  2. B 2.8 Correct answer
  3. C 7.8
  4. D 3.8

Solution

We know, <br><br>$qv = {{{p^2}} \over {2m}}$<br><br>$\Rightarrow p = \sqrt {2mqv}$<br><br>$\therefore$ $\lambda = {h \over {\sqrt {2mqv} }}$<br><br>$\therefore$ $${{{\lambda _p}} \over {{\lambda _\alpha }}} = {{\sqrt {2{m_\alpha }{q_\alpha }v} } \over {\sqrt {2{m_p}{q_p}v} }}$$<br><br>$= {{\sqrt {2(4m)(2e)} } \over {\sqrt {2me} }}$<br><br>$= \sqrt 8$<br><br>$= 2\sqrt 2$

About this question

Subject: Physics · Chapter: Dual Nature of Matter and Radiation · Topic: de Broglie Hypothesis

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