Expectant mothers many times see their unborn child for the first time during an ultrasonic examination. in ultrasonic imaging, the blood flow and heartbeat of the child can be measured using an echolocation technique similar to that used by bats. for the purposes of these questions, use 1500 m/s as the speed of sound in tissue. i need with part b and c

part a. to clearly see an image, the wavelength used must be at most 1/4 of the size of the object that is to be imaged. what frequency is needed to image a fetus at 8 weeks of gestation that is 1.6 cm long? i got 380 khz for part a

a. 380 khz

b. 3.8 khz

c. 85 khz

d. 3.8 mhz

part b. blood flow rates in the umbilical cord can be found by measuring the doppler shift of the ultrasound signal reflected by the red blood cells. if the source emits a frequency f, what is the measured reflected frequency fr? assume that all of the red blood cells move directly toward the source. let c be the speed of sound in blood and v be the speed of the red blood cells.

a. f(c+v)/v−c

b. f(c+v)/c−v

c. f(c+v)/c

d. f(c−v)/v+c

part c. ultrasonic imaging is made possible due to the fact that a sound wave is partially reflected whenever it hits a boundary between two materials with different densities within the body. the percentage of the wave reflected when traveling from material 1 into material 2 is r=(ρ1−ρ2ρ1+ρ2)2. knowing this, why does the technician apply ultrasound gel to the patient before beginning the examination?

a. the gel has a density similar to that of skin, so very little of the incident ultrasonic wave is lost by reflection.

b. the gel allows the instrument to slide more easily against the patient.

c. the gel provides a calibration density.

d. the sound waves do not dissipate through the gel.