Question

If $E_{A}, E_{B}$ and $E_{C}$ represent kinetic energies of an electron, alpha particle and proton respectively and each moving with same de-Broglie wavelength, then choose the correct increasing representation,

• A. $E_{A}=E_{B}=E_{C}$
• B. $E_{A} > E_{B} > E_{C}$
• C. $E_{B} > E_{C} > E_{A}$
• D. $E_{A} < E_{C} < E_{B}$

Answer 1

Answer: (D)

As we know that,
$\lambda=\frac{h}{m v}=\frac{h}{\sqrt{2 m KE }}$
$\because \lambda \propto \frac{1}{\sqrt{m}}$
Mass of $e, \alpha$ and $p$ are $m_{e} < m_{p} < m_{\alpha}$.
The correct order is $E_{A} < E_{C} < E_{B}$.