question_answer 35)

                  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) \[y=-0.4\,\sin \,\,2\pi \left( t-\frac{x}{2} \right)\]

Answer:

                  (b) Amplitude of reflected wave \[=0.6\,\times \frac{2}{3}\,=\,0.4\]                 There is a phase difference of p between the incident wave and reflected wave, when reflection occurs at denser medium.