How long will sound take to travel in (a) an iron rail and (b) air, both 3.3 km in length? Take speed of sound in air to be 330 m s^-1 and in iron to be 5280 m s^-1 .

Assuming the speed of sound in air equal to 340 m s^-1 and in water equal to 1360 m s^-1 , find the time taken to travel a distance 1700 m by sound in (i) air and (ii) water.

The speed of ultrasound in air is :

1. the same as audible sound
2. less than audible sound
3. more than audible sound
4. equal to the speed of light

Echo-cardiography is used to obtain the image of

1. lungs
2. liver
3. heart
4. kidney