Ultrasonic waves-
- AAre sound waves with a frequency less than 20 kHz
- BAre sound waves with a frequency greater than 20 kHz
- CAre sound waves with a frequency between 20 Hz and 20 kHz
- DAre electromagnetic waves
- ENone of the above/More than one of the above
Show answer and explanation
Correct answer: (b) Are sound waves with a frequency greater than 20 kHz
Explanation
Ultrasonic waves are sound waves with frequencies above 20 kHz, too high for humans to hear. Bats, dolphins and dogs can hear them.
Sound below 20 Hz is infrasonic, and 20 Hz to 20 kHz is the range humans hear. Ultrasound is used in SONAR and in medical scanning.