The rope shown at an instant is carrying a wave travelling towards right, created by a source vibrating at a frequency $n$. Consider the following statements
I.  The speed of the wave is $4n\times ab$.
II. The medium at a will be in the same phase as $d$ after $\frac{4}{3n}s$
III. The phase difference between $b$and $e$ is $\frac{3\pi }{2}$
Which of these statements are correct?

 

The diagram below shows the propagation of a wave. Which points are in same phase?

A progressive wave is represented by $y=12\sin (5t-4x)\mathrm{cm}.$ On this wave, how far away are the two points having phase difference of $90°?$ 

When sound is reflected from a denser medium,

When longitudinal waves are reflected from the surface of a rarer medium, 

When two sound waves with a phase difference of $\frac{\pi }{2}$ and each having amplitude $A$ and frequency $\omega$ are superimposed on each other, then the maximum amplitude and frequency of resultant wave is 

The displacement of the interfering light waves are $y_1=4\sin \omega t$ and $y_2=3\sin \left(\omega t+\frac{\pi }{2}\right)·$ What is the amplitude of the resultant wave? 

Two periodic waves of intensities $I_1$ and $I_2$ pass through a region at the same time in the same direction. The sum of the maximum and minimum intensities is