Question

Equation of plane progressive wave is given by $y=0.6sin2\pi (t-\frac{x}{2})$. 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. $y=0.6sin2\pi (t+\frac{x}{2})$
• B. $y=-0.4sin2\pi (t+\frac{x}{2})$
• C. $y=0.4sin2\pi (t+\frac{x}{2})$
• D. $y=-0.4sin2\pi (t-\frac{x}{2})$

Answer 1

The correct option is B $y=-0.4sin2\pi (t+\frac{x}{2})$

Amplitude of reflected wave $=\frac{2}{3}\times 0.6=0.4$
On reflection from a denser medium there is phase change of $\pi$.
$\therefore$ Equation of reflected wave is
$y=0.4sin2\pi (t+\frac{x}{2}+\pi )=-0.4sin2\pi (t+\frac{x}{2})$