65th B.P.S.C. (Re-Exam) (Pre) 2020
Ultrasonic waves-
aare sound waves with a frequency less than 20 kHz
bare sound waves with a frequency greater than 20 kHz✓ Correct
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
Explanation
Sound waves with a frequency greater than 20 kHz are called ultrasonic waves. Humans cannot hear this sound; however, some animals (dogs, cat, bat, etc.) can hear it. Ultrasonic waves can be produced using Galton's whistle.
general-science