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CSS Physics QUESTION #1173
Question 1
Alpha particles and electrons having the same energy — their associated De Broglie wavelengths are:
  • Equal
  • Longer than electrons (alpha has longer wavelength)
  • Smaller than electrons (alpha has shorter wavelength)✔️
  • None of these
Correct Answer Explanation
De Broglie wavelength: \(\lambda = \frac{h}{\sqrt{2mE}}\). At the same kinetic energy \(E\), \(\lambda \propto \frac{1}{\sqrt{m}}\). Since \(m_\alpha \gg m_e\) (alpha particle is ~7294 times heavier), \(\lambda_\alpha \ll \lambda_e\). So alpha particles have a much shorter De Broglie wavelength than electrons at the same energy.