Check Your Progress

Explain how cochlea converts the incoming sound waves into electrical signals.

Explain how cracks are determined in metal blocks.

Explain the technology of ultrasonography used in medical diagnosis.

Give reasons for the following:

We cannot hear any sound on vibrating our hands forward and backwards.

Give reasons for the following.

Owners of dogs use the Galton's whistle.

Using sonar, sound pulses are emitted at the surface. The pulses, after being reflected from the bottom, are detected. If the time interval from the emission to the detection of the sound pulses is $2$ seconds, find the depth of the water. (take velocity of sound through water, $v=1500 \mathrm{m}/\mathrm{s}$)

Two children are at opposite ends of an iron pipe. One strikes an end of the pipe with a stone. Find the ratio of times taken by the sound waves in air and in iron to reach the other child. (Take speed of sound in air at $20°\mathrm{C}=344 \mathrm{m}/\mathrm{s}$, speed of sound in iron at $20°\mathrm{C}=1530 \mathrm{m}/\mathrm{s}$)

Radiowaves sent from the earth towards the surface of moon are received back on the earth after reflection in $2.5$ seconds. If the velocity of radiowaves is $3\times {10}^8\mathrm{m}/\mathrm{s}$, calculate the distance of the moon from the earth.