Q. The amplitude of two waves are in ratio 5:2. If all other conditions for the two waves Are same, then what is the ratio of their energy densities?
A) 5:2
B) 5:4
C) 4:5
D) 25:4
Explanation
(d) Energy density of wave is given by
$u = 2\pi^{2}n^{2}\rho a^{2}$
Or $u \propto a^{2}\ \ \ \ \ \ \ \ \ \ (as\ n\ and\ \rho\ are\ consants)$
$\therefore\frac{u_{1}}{u_{2}} = \frac{a_{1}^{2}}{a_{2}^{2}} = \frac{5^{2}}{2^{2}}$
So, $u_{1}:u_{2} = 25:4$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.