Q. A sonar device on a submarine sends out a signal and receives an echo $5s$ later. Calculate the speed of sound in water if the distance of the object from the submarine is $3625m$.

Q. When a sound is reflected from a distinct 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?

Q. Describe with the help of a diagram, how compressions and rarefactions are produced in air near a source of sound?

Q. Explain how defects in a metal block can be detected using ultrasound.

Q. Does sound follow the same laws of reflection as light does? Explain.

Q. A stone is dropped from the top of a tower $500m$ high into a pond of water at the base of the tower. When is the splash heard at the top? Given, $g=10m{s}^2$ and speed of sound $=340m{s}^{-1})$.

Q. Which characteristics of the sound helps you to identify your friend by his voice while sitting with others in a dark room?

Q. Give two practical applications of reflection of sound waves.

Q. A sound wave travels at a speed of $339m{s}^{-1}$. If its wavelength is $1.5cm$. What is the frequency of the wave? Will it be audible?

Q. What is reverberation? How can it be reduced?

Q. Flash and thunder are produced simultaneously. But thunder is heard a few seconds after the flash is seen. Why?

Q. Why is sound wave called a longitudinal wave?

Q. The frequency of a source of sound is $100Hz$. How many times does it vibrate in a minute?

Q. How is ultrasound used for cleaning?

Q. 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.

Q. A person has a hearing range from $20Hz$ to $20KHz$. What are the typical wavelengths of sound waves in air corresponding ton these two frequencies? Take the speed of sound in air as $344m{s}^{-2}$.

Q. Explain the working and application of a sonar.

Q. What is sound and how is it produced?

Q. What is loudness of sound? What factors does it depend on?

Q. Cite an experiment to show that sound needs a material medium for its propagation :