Question:

An α particle and a carbon 12 atom has same kinetic energy K. The ratio of their de-Broglie wavelengths \((λ_α :λ_{C_{12}})\) is :

Updated On: Mar 19, 2025
  • 1: √3
  • √3 : 1
  • 3 : 1
  • 2 : √3
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The Correct Option is B

Solution and Explanation

\(K_α = K_C\)

\(\frac{p^2_α}{2m_α} = \frac{p^2_c}{2m_c}\)

\(\frac{pα}{pc} = \sqrt{ \frac{m_α}{m_c}}\)

Therefore,  \(\frac{λ_α}{λ_c} = \frac{h/p_α}{h/p_c} = \sqrt{\frac{m_c}{m_α}}\)

So \(\frac{λ_α}{λ_c} =\frac{ \sqrt3}{1}\)

Hence, the correct option is (B): \(\sqrt 3 : 1\)

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Concepts Used:

Kinetic Theory

The Kinetic Theory of Gases is a theory which explains the deviation of gas behaviour from ideal gases. 

Postulates of Kinetic Theory of Gases:

This theory states that:

  1.  The molecules of a gas are very small as compared to the distance between the molecules. 
  2. A gas consists of a large number of molecules. These molecules collide with each other and the walls of the container. They obey Newton's Laws. 
  3. There are no external forces acting on the molecules, apart from these elastic collisions.