Question

12/25 FOghorn Dn ighthouce 2. Foghorns [25pts) A lighthouse uses a foghorn to warn ships of the rocky coastline in poor visibility conditions. A ship approaching coastline at a speed of v 20.0m/s hears a frequency of f =50.0Hz. The lighthouse is at rest. What frequency would the ship hear if it were at rest? (5pt] a. Soffe -3 fLES2.9Hz = fc (CtVE fL fL=(50 0Hz(340me t 20 om/s 240m/s What frequency would the ship hear if it were moving away from the lighthouse? (5pts] b. fi-fs(CV fL-(C0DH2)(31Dm20 om/s FLE47 IHz Consttat If the Loudness of the foghorn at r 1.00m away is B= 120. dB. What is c the intensity, I, of this sound? (5pt) I I' B-ladB = I To 120 d B 00m I-DDm d In order to hear sound of the foghorn, the crew of the boat require the sound to have a loudness of at least B= 60.0d8. How far away can the foghorn be heard under these conditions? (10pt) I I r'=r I' I r'=1Oom2 Lo0 Odp 120 dB -5)

Answer 1

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