00:00Question says, the phase difference between two points separated by one meter in a wave
00:13of frequency 120 hertz is 90 degree.
00:18The wave velocity is a 180 meter per second, b 240 meter per second, c 480 meter per second,
00:30d 720 meter per second.
00:34As we have to find wave velocity, so wave velocity is calculated by formula v is equal to lambda
00:41into f. As frequency is given, but wavelength is not given, so first of all, we will find
00:52wavelength as we know that path difference delta x is calculated by using formula lambda
01:01upon 2 pi into phase difference. As we know that phase difference delta phi is given as
01:1690 degree, which is equal to pi upon 2 radian. We have to find wavelength as delta x means
01:28path difference is also given as 1 meter. So, to calculate the wavelength by putting these
01:38values, 1 is equal to lambda upon 2 pi into delta phi is equal to pi upon 2, so pi will be get
01:52cancelled with pi. So, 1 will be equal to lambda upon 2 into 2 it will be 4. So, here 4 is dividing
02:03on the other side of equal, it will multiply, so it will be 4 into 1 is equal to lambda or lambda
02:12is equal to 4 into 1, so 4 meter. As wavelength is obtained as 4 meter. Now finally, we will find
02:30wave velocity. As wave velocity is equal to v is equal to lambda into f. As lambda is obtained as 4 into
02:41f means frequency, which is obtained as 120 hertz. So, wave velocity will be equal to 480 meter per
02:54second. So, the correct option will be c 480 meter per second.
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