Ultrasound reflection occurs at an interface between media with a difference in:
a. temperature
b. Impedence
c. volume
d. mass

B

From a breast cancer detection website:
"Ultrasound imaging is based on acoustic impedance (a product of the
density of the observed tissue and the ultrasound velocity along that
tissue)."


Search Strategy:

how ultrasound works impedance on google:
://www.google.com/search?q=how+ultrasound+works+impedance


Additional Links:

Breast cancer detection website:
http://www.drgdiaz.com/breast_cancer_ultrasound.shtml


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