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

The speed of highly penetrating ultrasonic waves is:

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

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?

Which of the following are used to study the growth of fetus inside the mother's womb?