Question

The de-Broglie wavelength associated with an electron moving with a speed of $5.4 \times 10^{6} \,ms ^{-1}$ is

• A. $0.135 \,nm$
• B. $0.125 \,nm$
• C. $0.150 \,nm$
• D. $0.145\, nm$

Answer 1

Answer: (A)

For the electron,
Mass, $m=9.11 \times 10^{-31} kg$, speed
$v=5.4 \times 10^{-6} \,ms ^{-1}$
Then, momentum
$p=m v=9.11 \times 10^{-31} \times 5.4 \times 10^{6}$
$=4.92 \times 10^{-24}\, kg \,ms ^{-1}$
de-Broglie wavelength, $\lambda=\frac{h}{p}$
$=\frac{6.63 \times 10^{-34} Js }{4.92 \times 10^{-24} kgms ^{-1}}$
$=0.135\, nm$