Answer #45

The correct answer is A. In fact the Doppler shift is DIRECTLY proportional to the cosine of the angle of insonification and not inversely proportional. This question requires knowledge of the Doppler equation shown below [insert Doppler shift picture and equation]. As we can see the amount of shift is directly proportional to velocity of the object (Choice D is therefore incorrect), the frequency of the ultrasound transducer (Choice B is incorrect) as well as the cosine of the angle between the beam and moving object. The cosine of 0 degrees is 1 so at an angle of 0 degrees, we have the highest Doppler shift. Speed of ultrasound in a medium is in the denominator and so faster travel of the beam through a medium will mean less Doppler shift (Choice C is incorrect)