Q146 / 180 · COMEDK 2015 · Physics

The momentum of electrons having a wavelength $2 Å$ (given, $h=6.626 \times 10^{-34} \mathrm{~J}$-s, $\left.m=9.1 \times 10^{-35} \mathrm{~kg}\right)$ is

  • A
    $6.313 \times 10^{-24} \mathrm{~kg}^{-\mathrm{m} \mathrm{s}^{-1}}$
  • Correct answer
    B
    $3.313 \times 10^{-24} \mathrm{~kg}-\mathrm{m} \mathrm{s}^{-1}$
  • C
    $9.313 \times 10^{-25} \mathrm{~kg}-\mathrm{m} \mathrm{s}^{-1}$
  • D
    $12.313 \times 10^{-24} \mathrm{~kg}-\mathrm{m} \mathrm{s}^{-1}$

Solution

Given, $h=6.626 \times 10^{-34} \mathrm{~J}-\mathrm{s}$ $m=9.1 \times 10^{-35} \mathrm{~kg}$ Wavelength, $\lambda=2 Å$ $=2 \times 10^{-10} \mathrm{~m}$ $\therefore$ Momentum of electron is given as $$ \begin{aligned} p &=\frac{h}{\lambda} \\ &=\frac{6.626 \times 10^{-34}}{2 \times 10^{-10}}=3.313 \times 10^{-24} \mathrm{~kg}-\mathrm{ms}^{-1} \end{aligned} $$

Hence, the correct answer is option: 'B'.

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