Question

If the kinetic energy of a free electron is doubled, its De Broglie wavelength changes by the factor:

• A. $\sqrt{2}$
• B. $\frac{1}{\sqrt{2}}$
• C. $2$
• D. $1/2$

Answer 1

The correct option is B $\frac{1}{\sqrt{2}}$

As we know,
$\lambda =\frac{h}{mv}=\frac{h}{\sqrt{2mE}}$
so as KE doubles its De Broglie wavelength changes by
${\lambda }_2/{\lambda }_1=1/\sqrt{2}$