Answer #9

The correct answer is E: 385 micrometers. Recall the range of diagnostic ultrasound is 77 to 770 micrometers. Knowing this alone one can answer the question without having to do any calculations. To calculate this directly we use the formula that wavelength = 1540m/s (the average speed of ultrasound in tissue)/ frequency which is 1540m/second/4MHz = 385 micrometers. None of the other answers A-D make sense and are orders of magnitude off.