CBSE 2022 · Region 3 · Set 1 · Q9 · 3 marks
An electron is accelerated from rest through a potential difference of $\displaystyle 100$ V. Find :(i)the wavelength associated with(ii)the momentum of and(iii)the velocity required by, the electron.
An electron is accelerated from rest through a potential difference of $\displaystyle 100$ V. Find :
(i)
the wavelength associated with
(ii)
the momentum of and
(iii)
the velocity required by, the electron.
Marking-scheme solution
(i)
Finding Wavelength & $\displaystyle 1$
(ii)
Finding Momentum & $\displaystyle 1$
(iii)
Finding Velocity & $\displaystyle 1$
(i)
$$\begin{aligned}
\lambda & =\frac{1 \cdot 23}{\sqrt{V}} \mathrm{~nm}=\frac{1.23}{\sqrt{100}}
& =$\displaystyle 0$ \cdot $\displaystyle 123$ \mathrm{~nm}
\end{aligned}
$$(ii) $\displaystyle p=\frac{h}{\lambda}$
$$\begin{aligned}
& =\frac{$\displaystyle 6.63$ \times $\displaystyle 10$^{-$\displaystyle 34$}}{$\displaystyle 0.123$ \times $\displaystyle 10$^{-$\displaystyle 9$}}
& =$\displaystyle 5.4$ \times $\displaystyle 10$^{-$\displaystyle 24$} \mathrm{~kg} \mathrm{~m} \mathrm{~s}^{-$\displaystyle 1$}
\end{aligned}
$$(iii) $\displaystyle v=\frac{p}{m}$
$$v=\frac{$\displaystyle 5.4$ \times $\displaystyle 10$^{-$\displaystyle 24$}}{$\displaystyle 9$ \cdot $\displaystyle 1$ \times $\displaystyle 10$^{-$\displaystyle 31$}}
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CBSE Class 12 Physics past-paper question from the 2022board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.