Question:

An electron, helium ion (\( \text{He}^{++} \)) and proton having the same kinetic energy. The relation between their respective de-Broglie wavelengths \( \lambda_e, \lambda_{\text{He}^{++}} \) and \( \lambda_p \) is

Show Hint

For same KE: wavelength depends only on mass $\longrightarrow$ lighter particle = larger wavelength.
Updated On: Apr 22, 2026
  • \( \lambda_e>\lambda_p>\lambda_{\text{He}^{++}} \)
  • \( \lambda_e>\lambda_{\text{He}^{++}}>\lambda_p \)
  • \( \lambda_e<\lambda_p<\lambda_{\text{He}^{++}} \)
  • \( \lambda_e<\lambda_{\text{He}^{++}} = \lambda_p \)
Show Solution
collegedunia
Verified By Collegedunia

The Correct Option is A

Solution and Explanation

Concept: De-Broglie wavelength: \[ \lambda = \frac{h}{\sqrt{2mK}} \Rightarrow \lambda \propto \frac{1}{\sqrt{m}} \]

Step 1:
Compare masses.
\[ m_e \ll m_p<m_{\text{He}^{++}} \]

Step 2:
Apply relation.
Smaller mass \(\Rightarrow\) larger wavelength.

Step 3:
Final order.
\[ \lambda_e>\lambda_p>\lambda_{\text{He}^{++}} \]
Was this answer helpful?
0
0