MCQ
Electrons are accelerated through a potential difference $V$ and protons are accelerated through a potential difference $4\, V$. The de-Broglie wavelengths are $\lambda_e $ and $\lambda_p $ for electrons and protons respectively. The ratio of $\frac{{{\lambda _e}}}{{{\lambda _p}}}$ is given by : (given $m_e$ is mass of electron and $m_p$ is mass of proton).
  • A
    $\frac{{{\lambda _e}}}{{{\lambda _p}}} = \sqrt {\frac{{{m_p}}}{{{m_e}}}} $
  • B
    $\frac{{{\lambda _e}}}{{{\lambda _p}}} = \sqrt {\frac{{{m_e}}}{{{m_p}}}} $
  • C
    $\frac{{{\lambda _e}}}{{{\lambda _p}}} = \frac{1}{2}\sqrt {\frac{{{m_e}}}{{{m_p}}}} $
  • $\frac{{{\lambda _e}}}{{{\lambda _p}}} = 2\sqrt {\frac{{{m_p}}}{{{m_e}}}} $

Answer

Correct option: D.
$\frac{{{\lambda _e}}}{{{\lambda _p}}} = 2\sqrt {\frac{{{m_p}}}{{{m_e}}}} $
d
Energy in joule $(E)$

$=$ charge $\times$ potential diff. in volt

${{\text{E}}_{{\text{electron }}}} = {q_{\text{e}}}{\text{V}}$ and ${{\text{E}}_{{\text{proton }}}} = {q_{\text{p}}}4{\text{V}}$

de-Broglie wavelength

$\lambda=\frac{\mathrm{h}}{\mathrm{P}}=\frac{\mathrm{h}}{\sqrt{2 \mathrm{mE}}}$

$\lambda_{\mathrm{c}}=\frac{\mathrm{h}}{\sqrt{2 \mathrm{m}_{\mathrm{e}} \mathrm{e} \mathrm{V}}}$ and $\lambda_{\mathrm{P}}=\frac{\mathrm{h}}{\sqrt{2 \mathrm{m}_{\mathrm{p}} \mathrm{e} 4 \mathrm{V}}}$

${\text{(}}\because {q_c} = {q_p}{\text{)}}$

$\therefore \frac{{{\lambda _{\text{c}}}}}{{{\lambda _{\text{P}}}}} = \frac{{\frac{{\text{h}}}{{\sqrt {2{{\text{m}}_{\text{e}}}{\text{eV}}} }}}}{{\frac{{\text{h}}}{{\sqrt {2{{\text{m}}_p}{\text{e4V}}} }}}}$ $ = \sqrt {\frac{{2{{\text{m}}_p}{\text{e4V}}}}{{2{{\text{m}}_e}{\text{eV}}}}} $

$ = 2\sqrt {\frac{{{{\text{m}}_{\text{p}}}}}{{{{\text{m}}_{\text{e}}}}}} $

Need a full question paper?

Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.

Start Generating Free

Similar questions

The echo of a gun shot is heard $8\, sec$. after the gun is fired. How far from him is the surface that reflects the sound .... $m$ (velocity of sound in air $= 350 \,m/s$)
A flywheel rotates with a uniform angular acceleration. Its angular velocity increases from $20\pi \, rad/s$ to $40\pi \,rad/s\,m\,10\,sec$ . How many rotations did it made in this period
In the forward bias arrangement of a $PN-$junction diode
Choose the Gattermann-Koch reaction :-
Unit vector parallel to the resultant of vectors $\vec A = 4\hat i - 3\hat j$and $\vec B = 8\hat i + 8\hat j$ will be
Ball $A$ is thrown up vertically with speed $10 \,m / s$. At the same instant another ball $B$ is released from rest at height h. At time $t$, the speed of $A$ relative to $B$ is ...........
$X-$ ray beam of intensity ${I_0}$ passes through an absorption plate of thickness $d$. If absorption coefficient of material of plate is $\mu $, the correct statement regarding the transmitted intensity $I$ of $X-$ ray is
A tungsten body of diameter $2.3\, cm$ is at $2000\,^oC$. It radiates $30\%$ of the energy radiated by a black body of same radius and temperature. Find radius of black body which will radiate energy at same rate at the same temperature......... $cm$
A wave travelling in the $+ve$ $x-$ direction having displacement along $y-$ direction as $1\,\, m,$ wavelength $2\pi\,\, m$ and frequency of $\frac{1}{\pi}$ $Hz$ is represented by
A sound source is moving on a circular path of radius $R$ with constant angular speed $\omega $ in anticlockwise direction and emits a frequency $n$ . An observer performs simple harmonic along the path $QPR$ with time period $T = \frac {2\pi }{\omega }$ as shown in the figure. If at $t = 0$ source is at $A$ and observer is at $Q$ and assume $OP$ is very large as compare to radius $R$ and $QP$ , then