Question

If $E_e,E_{\alpha },E_p$ represents the kinetic energies of an electron, alpha particle and a proton respectively, each moving with same de-Broglie wavelength then:

• A. $E_e=E_{\alpha }=E_p$
• B. $E_e>E_{\alpha }>E_p$
• C. $E_{\alpha }>E_p>E_e$
• D. $E_e>E_p>E_{\alpha }$

Answer 1

The correct option is D $E_e>E_p>E_{\alpha }$

$\lambda =\frac{h}{\sqrt{2mE}}$
For constant wavelength, kinetic energy is also inversely proportional to the mass.
$m_{\alpha }>m_p>m_e$
Hence, order of kinetic energy is
$E_e>E_p>E_{\alpha }$