1.

A wave travels on a light string. The equation of the waves is `y= A sin (kx - omegat + 30^@)`. It is reflected from a heavy string tied to an end of the light string at x = 0. If 64% of the incident energy is reflected, then the equation of the reflected wave isA. `y = 0.8 A sin (kx - omegat + 30^@ + 180^@)`B. `y = 0.8 A sin (kx + omegat + 30^@ + 180^@)`C. `y= 0.8 A sin (kx - omegat - 30^@)`D. `y= 0.8 A sin (kx - omegat + 30^@)`

Answer» Correct Answer - B
`I prop A^2`
` I_r = 0.64 I_i`
` :. A_r = 0.8 A_i`
` = 0.8 A `
Reflected from a denser medium. Hence, a phase
change of `pi` will occur. Reflected wave will travel
in opposite direction. Hence, `omegat and kx` will have
positive signs.


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