In ripple tank, 40 waves pass through a certain point in one second. If distance between two consecutive in phase points of the waves is 5 cm. Then, find the speed of wave.
Correct answer: D. 2 ms-1
- A. 2.7 ms-1
- B. 3 ms-1
- C. 200 ms-1
- D. 2 ms-1
Explanation
Number of waves passing through a certain point in 1 second = 40 waves The wavelength of the wave (λ)= cm Find:Wave speed. Solution: Let the speed of the wave be 'v'. The frequency of a wave is equal to the number of waves passing through a given point per unit of time. The wavelength of a wave is equal to the distance between two consecutive peaks or two consecutive troughs. It is denoted by 'λ'.The speed of a wave is equal to the product of its frequency (f) and its wavelength (λ) In the given question: the wavelength of the wave (λ) = 5 cm = 0.05 m Since 40 waves pass through a certain point in 1 second, the frequency of the wave would be 40 Hz. Wave speed(v)=frequency(f)×wavelength(λ) Hence V= Fλ Hence v= 40×0.05 Therefore, v=m/s Therefore, the speed of the wave is equal to 2m/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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