Question

De-Broglie wavelength of an electron travelling with speed equal to $1$% of the speed of light is?

• A. $400pm$
• B. $120pm$
• C. $242pm$
• D. $375pm$

Answer 1

The correct option is C $242pm$

According to De-Broglie relation:
$\lambda =\frac{h}{mv}$---$\left(i\right)$
Mass of electron = $9.1\times {10}^{-31}$ kg
Velocity is 1% the speed of light
i.e $v=c\times \frac{1}{100}=3\times {10}^8\times 0.01=3\times {10}^{6}m/s$
Putting all the values in $\left(i\right)$ gives,
$\lambda =\frac{6.6\times {10}^{-34}}{9.1\times {10}^{-31}\times 3\times {10}^6}$
$=0.242m$ or
$\Rightarrow$ $\lambda =242pm$.