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Physics · KINETIC THEORY
हिन्दीA polyatomic gas molecule has 3 translational, 3 rotational degrees of freedom, and \( f \) vibrational modes. If the adiabatic index of the gas is \( \gamma = 1.25 \), what is the number of vibrational modes \( f \)?
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Correct answer · Option A
1
Explanation
For polyatomic gas with \( f \) vibrational modes: \( C_v = (3 + f)R \), \( C_p = (4 + f)R \). Thus \( \gamma = \frac{4 + f}{3 + f} = 1.25 = \frac{5}{4} \). Cross-multiplying: \( 4(4 + f) = 5(3 + f) \implies 16 + 4f = 15 + 5f \implies f = 1 \).
