Asked in PMC Practice Test 22 (2021) 2021Moderate

The shortest distance between two points on a travelling wave that have a phase difference of (pi/3) is 5 cm. If the wave has frequency 500 Hz, what is the speed of the wave?

Correct answer: B. 150 m/s

  • A. 300 m/s
  • B. 150 m/s
  • C. 300 cm/s
  • D. 150 cm/s

Explanation

For wavelength, According to the formula of Phase Difference = 2 / where, = phase difference ( phase angle between two points ) = wavelength of wave = path difference ( distance between two points on wave ) So, = 2 / / 3 = 2 / 5 / 3 = 2 5 = 10 3 = 30 cm For speed of wave, v = f where, v = speed of wave f = frequency = wavelength of wave So, v = f v = 500 30 v = 15000 cm/s NOTE we convert cm/s m/s ( dividing by 100) 15000 cm/s 150 m/s

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About Wave Speed

Wave speed is the rate at which a disturbance or wave pattern travels through a medium, given by v = fλ, where f is frequency and λ is wavelength. Questions examine how speed changes between media, the relation among frequency, wavelength and period, and why wave speed is not the same as particle vibration speed.

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