A sound wave travels at a speed of $339$ m s$^{-1}$. If its wavelength is $1.5$ cm, what is the frequency of the wave? Will it be audible?
2.
Explain how defects in a metal block can be detected using ultrasound.
3.
Which characteristic of the sound helps you to identify your friend by his voice while sitting with others in a dark room?
4.
Why is sound wave called a longitudinal wave?
5.
The frequency of a source of sound is $100$ Hz. How many times does it vibrate in a minute?
6.
A person has a hearing range from $20$ Hz to $20$ kHz. What are the typical wavelengths of sound waves in air corresponding to these two frequencies? Take the speed of sound in air as $344$ m s$^{-1}$.
7.
Two children are at opposite ends of an aluminium rod. One strikes the end of the rod with a stone. Find the ratio of times taken by the sound wave in air and in aluminium to reach the second child.
8.
Describe with the help of a diagram, how compressions and rarefactions are produced in air near a source of sound.
9.
Flash and thunder are produced simultaneously. But thunder is heard a few seconds after the flash is seen, why?
10.
What is sound and how is it produced?
11.
How is ultrasound used for cleaning?
12.
When a sound is reflected from a distant object, an echo is produced. Let the distance between the reflecting surface and the source of sound production remains the same. Do you hear echo sound on a hotter day?
13.
Does sound follow the same laws of reflection as light does? Explain.
14.
A stone is dropped from the top of a tower $500$ m high into a pond of water at the base of the tower. When is the splash heard at the top? Given, $g = 10$ m s$^{-2}$ and speed of sound = $340$ m s$^{-1}$.
15.
What is reverberation? How can it be reduced?
16.
What is loudness of sound? What factors does it depend on?
17.
Give two practical applications of reflection of sound waves.
