Question

Calculate de-Broglie wavelength of an electron travelling at $1\% $of the speed of light:

• A. $ 2.73\times 10^{-24}$
• B. $ 2.42\times 10^{-10} $
• C. $ 242.2\times 10^{10} $
• D. none of these

Answer 1

Answer: (B)

Use the following formula to find the answer:
$\lambda=\frac{h}{p}$ where,
$\lambda=$ de-Broglie wavelength
$h=$ Plancks constant
$=6.626 \times 10^{-34} Js$
$p=m v$ where $m=9.11 \times 10^{-31} kg$
$\left.v=\frac{1}{100} \times\left(3 \times 10^{8}\right) ms ^{-1}\right)$
$=3 \times 10^{6} ms ^{-1}$
$\therefore \lambda=\frac{6.626 \times 10^{-3}}{9.110^{31} \times 3 \times 10^{6}}$
$=2.424 \times 10^{-10}$