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Highly selective Backlog Qs for JEE MainPhysicsKinetic Theory of Gases

Assertion : Vibrational energy of diatomic molecule corresponding to each degree of freedom is k_B T . Reason : For every molecule, vibrational degree of freedom is 2 .

Options

  1. AIf both assertion and reason are true and reason is the correct explanation of assertion.
  2. BIf both assertion and reason are true but reason is not the correct explanation of assertion.
  3. CIf assertion is true but reason is false.
  4. DIf both assertion and reason are false.

Correct answer

C. If assertion is true but reason is false.

Step-by-step solution

According to law of equipartition of energy, in thermal equilibrium, at temperature T , each degree of freedom of translational, rotational and vibrational motion contributes an average energy equal to 1 2 k_B T . The vibrational motion has two types of energy associated with the vibrations along the length of the molecule-kinetic energy and potential energy. Thus, it contributes two degrees of freedom. Thus vibrational energy =2 1 2 k_B T=k_B T

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