PHYSICS [2 Mark Question Answer]

Two applications of ultrasound:
(i) Ultrasound is used for drilling holes or making cuts of desired shape in materials like glass.
(ii) Ultrasound is used in surgery to remove cataract and in kidneys to break the small stones into fine grains.

A ship sends ultrasonic waves downward in the ocean. When the sound waves reaches the ocean floor , they are reflected back to the ship . The time it takes for the signal to return is used to calculate the depth of submerged ship in the ocean.

Echolocation is defined as sending out sounds to judge the location, size, and motion of objects from the returning echoes. The animals use this phenomenon to locate the obstacles in their path and avoid them so it helps them in navigation and to locate their prey.

The simple experiment that a person can do to calculate the speed of sound in air is that a person stands at a known distance (d meter) from the cliff and fires a pistol and simultaneously start the stopwatch. He stops the stop-watch as soon as he hears an echo. The distance traveled by the sound during the time (t) seconds is 2d.
So, speed of sound = distance travelled / time taken = 2d/t

A person hearing at one end of the long metal bar hears two distinct sounds when the other end is struck with a stone because the sound comes from the metal bar as well as from the air. The sound travels faster in solids than air. So, the first sound comes from metal bar hitting and then from the air.

Speed of sound in air is directly proportional to the temperature of the air. As the temperature of air increases, the density of air decreases, and hence speed of sound increases.

Ultrasonic sound is the sound having frequency more than 20KHz. The application of ultrasonic sound is as follows:
(i) It is used to detect the flaws in metal casting of automobile tyres.
(ii) Used in hospitals to detect defects in certain parts of the body.

The simple experiment that a person can do to calculate the speed of sound in air is that a person stands at a known distance (d meter) from the cliff and fires a pistol and simultaneously start the stopwatch. He stops the stop-watch as soon as he hears an echo. The distance traveled by the sound during the time (t) seconds is 2d.
So, speed of sound = distance travelled / time taken = 2d/t

Yes, light travels faster in the air than water. Because light does not require any medium for their propagation and they are not mechanical waves. The quantities which oscillate in light are mechanical and electric fields. And electric and magnetic fields decrease with the medium in between them. So, light travels faster in the air than water.

With an increase in temperature of the gas, there is increase in the speed of gas because an increase in temperature decreases the density of a gas. And the speed of sound is inversely proportional to the density of the gas. The speed of the gas is independent of the pressure of the gas.

Sound is produced by the vibrating objects. We require a material medium for the propagation of sound because vibrations of object need to get transferred or transmitted from one place to another.

Yes, the speed of sound depends on the direction of wind. When wind is blowing in the direction of propagation of sound , the speed of sound increases. But, when wind blows in the direction opposite to that of sound , the speed of sound decreases.