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
$=6.626\times 10^{-34}Js$
$p=mv$ where $m=9.11\times 10^{-31}kg$
$v=\frac{1}{100}\times \left(3\times 10^8\right)m{s}^{-1})$
$=3\times 10^{6}m{s}^{-1}$
$\therefore \lambda =\frac{6.626\times 10^{-3}}{9.110^{31}\times 3\times 10^6}$
$=2.424\times 10^{-10}$