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Home / Doubts and Solutions/CBSE/Class 9/Physics

The figure given below shows the sound navigation system. It takes 2 s to record the echo of SONAR. If the speed of sound in water is 1450 m/s. Find out

  1. the depth of the floor
  2. wavelength of ultrasonic waves if the frequency is 20 kHz.

     

Asked by Topperlearning User 20th September 2016, 10:36 AM
Answered by Expert
Answer:
  1. Given that it takes 2 s to record the echo of SONAR.
    So, the time taken by the ultrasound to travel from the ship to the sea bed will be half this time, which is begin mathsize 12px style fraction numerator 2 straight s over denominator 2 end fraction equals 1 space straight s end style
    begin mathsize 12px style Now comma space Speed equals Distance over Time rightwards arrow Distance equals Speed space cross times space Time space space space space space space space space space space space space space space space space space equals 1450 space straight m divided by straight s space cross times space 1 space straight S rightwards arrow Distance equals 1450 space straight m divided by straight s end style

  2.  Given that frequency = 20 kHz
    Speed = Frequency × Wavelength
    1450 = 20 × λ
    → λ = 72.5 m
Answered by Expert 20th September 2016, 12:36 PM
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