being heard (speed of light-3.0x 108 ms, speed sound in air = 330 m s-1). (a) De

Question

being heard (speed of light-3.0x 108 ms, speed sound in air = 330 m s-1). (a) Define intensity of a wave. (b) The intensity of a water wave of amplitude 2 5 .0 m is m. Estimate the intensity of a water wave of amplitude 1.2 m if the frequency and wave speed are the same (c) Estimate the power of a wave of intensity 2.0 x 102 w m-2 as it passes through an opening 20 m long and 5 m high in a breached wall. Prior to the arrival of a tsunami wave, persons on the shore can see the bottom of the sea for considerable distances (Figure 8.22). Tsunami waves typically have wavelengths of 250 km and travel at jet plane sneede

Explanation / Answer

Let us go to the basics first.

Answer (2a): In physics, intensity is the power transferred per unit area, where the area is measured on the plane perpendicular to the direction of propagation of the energy. In the SI system, it has units watts per square metre (W/m2). It is used most frequently with waves (e.g. sound or light), in which case the average power transfer over one period of the wave is used.

Answer (2b): We know that intensity I is given by following relation:

I = (1/2)(C)(A)2  [where, =density of water medium; C = wave speed; A = amplitude; = frequency]

Thus, I1 = (1/2)(C)(A1)2

& I2 = (1/2)(C)(A2)2

Thus, I1 / I2 = A12/A22

=>(2*102)/ I2 = 52/1.22

=>(2*102)/ I2 = 52/1.22

=> I2 = 11.52 Wm-2 (Answer => Intensity of water wave)

Answer(2c):We also know that intensity I is given by following relation:

I = Power/Area

=> 2*102 = Power / (20*5)

=>Power = 20000 W (Answer)

Thanks!!!

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