Answer #8

The correct answer is B: 3 MHz. To answer this question you need to know that frequency = 1/period. In this case 1/33.3 x 10^-8 seconds. It helps to convert this to microseconds since we want to deal with megahertz (MHz) ultimately. Remember, the range for diagnostic ultrasound is 2 to 20 MHz). So we can use 0.333 x 10^-6 seconds as the period. The frequency is therefore 1/.333*10^-6 which is 3 MHz. None of the other answers are correct and you have enough information from what is given to answer the question.