Question

If the momentum of an electron is changed by $P$ , then the de-Broglie wavelength associated with it changes by $0.5\%$ . The initial momentum of electron will be,

• A. $200P$
• B. $400P$
• C. $\frac{P}{200}$
• D. $100P$

Answer 1

Answer: (A)

The de-Broglie wavelength associated with an electron is,
$\lambda =\frac{h}{P}$ ,
or, $P=\frac{h}{\lambda }$ ,
$\therefore \frac{\Delta P}{P}=-\frac{\Delta \lambda }{\lambda }$
$\Rightarrow \frac{P}{P_{\text{initial}}}=\frac{0 . 5}{100}$
Therefore,
$P_{\text{intial}}=200P$