Question

The de brogile wavelength of an electron whose speed is half of light is

• A. $3.6\times {10}^{-12}m$
• B. $4.2\times {10}^{-12}m$
• C. $8.4\times {10}^{-12}m$
• D. $0.12\times {10}^{-12}m$

Answer 1

Answer: (B)

$4.2\times {10}^{-12}m$

$\begin{array}{c}\text{Speed}=\frac{c}{2}=1.5\times {10}^8\\ \lambda =\frac{h}{mx}=\frac{6.6\times {10}^{-34}}{9.1\times {10}^{-31}\times 1.5\times {10}^8}\\ =\frac{6.6}{9.1\times 1.5}\times {10}^{-11}\\ =0.42\times {10}^{-11}\\ =4.2\times {10}^{-12}m\end{array}$