Question

If the following matter waves are travelling with same speeds, the longest wavelength is for

• A. An alpha particle
• B. A neutron
• C. A proton
• D. An electron

Answer 1

Answer: (D)

de-Broglie equation, $\lambda =\frac{h}{mv}$
v= constant
$\therefore \lambda \propto \frac{1}{m}$
Correct order of masses : $m_{\alpha }>m_n>m_p>m_e$
$\therefore$ correct order of wavelength : ${\lambda }_{\alpha }<{\lambda }_n<{\lambda }_p<{\lambda }_e$