Assume you have a circular 0.1m diameter dual frequency transducer 50/200 khz operating with peak output power of 4000w peak (500w rms) in shallow 60ft water assuming a back scattering coefficient of -15db, absorption coefficient of-3db and a fixed incident (look) angle of 20 degrees. assume vs = 1,495.5 m. s1, the source level of 145db, the noise level of 4db, and the ideal sea surface conditions. compute the return echo power (in db) for the a) low frequency beam b) high frequency beam, and c) compute the pulse length for a pulse rate of 0.5milliseconds for the high frequency beam [hint: pulse length is defined as lp = nc'x where the number of cycles nc = r'f for the pulse rate r ] where i ix a and a=2-r2