What are ultrasonic waves? Explain two applications.

What is Sonar? Explain.

How is sound produced?

What are echoes and how are they formed?

The audible frequency range of a human ear is $20 \mathrm{Hz}-20 \mathrm{kHz}$. Convert this into the corresponding wavelength range. Take the speed of sound in air at ordinary temperature to be $340 \mathrm{m}/\mathrm{s}$.

A bat emits ultrasonic sound of frequency $100 \mathrm{kHz}$ in air. If this sound meets a water surface, what is the wavelength of (a) the reflected sound (b) the transmitted sound? Speed of sound in air$=340 \mathrm{m}/\mathrm{s}$ and in water$=1486 \mathrm{m}/\mathrm{s}$. 

A hospital uses an ultrasonic scanner to locate tumours in a tissue. What is the wavelength of sound in a tissue in which the speed of sound is $1.7 \raisebox{1ex}{$\mathrm{km}$}\!\left/ \!\raisebox{-1ex}{$\mathrm{s}$}\right.$? The operating frequency of the scanner is $4.2 \mathrm{MHz}$. 

A vibrating body with constant frequency sends waves $0.2 \mathrm{m}$ long through the medium A and $0.25 \mathrm{m}$ long through medium B. If velocity of waves, in medium A is $280 \mathrm{m}/\mathrm{s}$, what is the velocity of the waves in medium B?

The shortest wavelength of the ultrasonic waves that a bat emits is approximately $3.32 \mathrm{mm}$ at $0°\mathrm{C}$. What is the frequency of these waves? Velocity of sound in air at $0°C = 332 \mathrm{m}/\mathrm{s}$