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Physics · 2022 · 3 marks
CBSE 2022 · Region 5 · Set 2 · Q5
An alpha particle is accelerated through a potential difference of 100 V. Calculate: (i) The speed acquired by the alpha particle, and (ii) The…
An alpha particle is accelerated through a potential difference of $\displaystyle 100$ V. Calculate :
(i)
The speed acquired by the alpha particle, and
(ii)
The de-Broglie wavelength associated with it. (Take mass of alpha particle $\displaystyle =6.4 \times 10^{-27} \mathrm{~kg}$ )
Marking-scheme solution
(i)
$\displaystyle \mathrm{V}=\sqrt{\frac{2 q V}{m}}$
$$\begin{aligned}
& =\sqrt{\frac{$\displaystyle 2$ \times $\displaystyle 2$ \times $\displaystyle 1.6$ \times $\displaystyle 10$^{-$\displaystyle 19$} \times $\displaystyle 100$}{$\displaystyle 6.4$ \times $\displaystyle 10$^{-$\displaystyle 27$}}}
& \quad=$\displaystyle 1$ \times $\displaystyle 10$^{$\displaystyle 5$} \mathrm{~m} / \mathrm{s}
\end{aligned}
$$ii) $\displaystyle \lambda=\frac{h}{p}=\frac{h}{m v}$
$$\begin{aligned}
& =\frac{$\displaystyle 6.63$ \times $\displaystyle 10$^{-$\displaystyle 34$}}{$\displaystyle 6.4$ \times $\displaystyle 10$^{-$\displaystyle 27$} \times $\displaystyle 10$^{$\displaystyle 5$}}
& \lambda=$\displaystyle 10$^{-$\displaystyle 12$} \mathrm{~m}
\end{aligned}
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