Which of the following is a commonly used backing material for continuous wave Doppler transducers?

A transducer with a large bandwidth is likely to have

Which of the following terms describes the change in direction of an ultrasonic beam when it passes from one medium to another in which elasticity and density differ from those in the first medium? 

Which of the following ultrasound frequency spectrum is specifically equal to operating frequency divided by bandwidth? 

Transducers may be focused by internal focusing and external focusing.  These are accomplished by

Rayleigh scattering occurs if the particle dimensions are 

An increase in reflection amplitude from reflectors that lie behind a weakly attenuating structure is called

Enhancement is caused by 

The amount of dispersion in the far field of an ultrasound beam can be decreased by

Improper location of an echo may be attributable to