\(\frac{I_0}{2}\)
\(\frac{I_0}{4}\)
\(\frac{I_0}{8}\)
Relation between intensities is \(I_R=\big(\frac{I_0}{2}\big)cos^2 (45^\circ)\)
\(=\frac{I_0}{2} \times \frac{1}{2}=\frac{I_0}{4}\)
Therefore, The correct answer is (C) : \(\frac{I_0}{4}\)
Consider the sound wave travelling in ideal gases of $\mathrm{He}, \mathrm{CH}_{4}$, and $\mathrm{CO}_{2}$. All the gases have the same ratio $\frac{\mathrm{P}}{\rho}$, where P is the pressure and $\rho$ is the density. The ratio of the speed of sound through the gases $\mathrm{v}_{\mathrm{He}}: \mathrm{v}_{\mathrm{CH}_{4}}: \mathrm{v}_{\mathrm{CO}_{2}}$ is given by