Answer #11

The correct answer is D: One cycle per 0.001 seconds.

The normal range of frequency of typical diagnostic ultrasound is 2 to 12 Megahertz (MHz or 10^6 cycles per second) so choice A is out since it falls within this range. For the others we must convert them to frequencies on the MHz scale.

Gigahertz (GHz) is 10^9 cycles per second, and 0.01 GHz is equal to 10 MHz so choice E is eliminated.

Frequency is the inverse of period. Period gives the time per cycle. Frequency is the number of cycles per second. So 1 divided by 0.2 microseconds per cycle (or 1/0.2x 10^-6) is the same as 5 x 10^6 or 5 million cycles per second which is 5 MHz. So choice B is out.

3,000 Kilohertz (KHz or 10^3 cycles per second) is the same as 3 MHz so choice C is out.

This leaves choice D. One cycle per second 0.001 seconds is the same as saying there are 1000 cycles in 1 second. This is only 1 KHz and is not in the range of diagnostic ultrasound.