The frequencies of four sound waves are given below. Which of these sound waves can be used to measure the depth of sea by the echo method?

A. 15,000 Hz B. 10 kHz

C. 50 kHz D. 10,000 Hz

The speed of highly penetrating ultrasonic waves is:

A. lower than those of audible sound waves

B. higher than those of audible sound waves

C. much higher than those of audible sound waves

D. same as those of audible sound waves

The ultrasound waves can penetrate into matter to a large extent because they have :

A. very high speed

B. very high frequency

C. very high wavelength

D. very high amplitude

Which of the following frequency of sound can be generated by a vibrating simple pendulum as well as by the vibrating vocal cords of a rhinoceros?

A. 5 kHz B. 25 Hz

C. 10 Hz D. 15,000 Hz

Which of the following device does not work on the multiple reflections of sound waves?

A. stethoscope B. hydrophone

C. soundboard D. megaphone