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14.Waves and Sound
normal
Equation of a plane progressive wave is given by $y = 0.6\sin 2\pi \left( {t - \frac{x}{2}} \right)$. On reflection from a denser medium its amplitude becomes $2/3$ of the amplitude of the incident wave. The equation of the reflected wave is
A
$y = 0.6\sin 2\pi \left( {t + \frac{x}{2}} \right)$
B
$y = - 0.4\sin 2\pi \left( {t + \frac{x}{2}} \right)$
C
$y = 0.4\sin 2\pi \left( {t + \frac{x}{2}} \right)$
D
$y =-0.4\sin 2\pi \left( {t - \frac{x}{2}} \right)$
Solution
– On reflection from a denser medium, there is a phase reversal of $180^{\circ}$.
New amplitude $=\frac{2}{3} \times 0.6=0.4$
$\therefore$ Equation of reflected wave is
$-y=0.4 \sin 2 \pi\left[t+\frac{x}{2}+180^{\circ}\right]=-0.4 \sin 2 \pi(t+x / 2)$
Standard 11
Physics
