Sound Test - 9

Like light, sound waves also get reflected at the surface of a solid or liquid and follow the laws of reflection.
 Laws of reflection: (a) Angle of incidence is equal to the angle of reflection. (b) The incident ray, the reflected ray and normal at the point of incidence all lie in the same plane.

The good directional property of ultrasound waves are used for scanning objects and is used in the detection of cracks.

Speed of sound = 346 ms^-1 

Time taken =5sec.5sec.

Since,

distancedistance  =speed×time=speed×time.

⟹ 2d = 346 × 5

⟹ 2d = 1730 

⟹ d = 865m

Rolling thunder is repeated claps of thunder in quick succession. The sound of same loudness and pitch produced by two different sources can be distinguished by timbre. Female's voice has more frequency components compared to men. Women speak at one octave higher than men.
So, statement (A) is false and (B) and (C) are correct statement.

During thunderstorm, we observe lightening first and hears the sound of thunder later, although both occurs simultaneously because light travels much faster than sound.The speed of sound through air is about 340 ms^-1. The speed of light in air is about 300 million meters per second. Therefore,light travels faster than sound.

Stethoscope is used to hear the sounds of internal organs of a patient; for diagnostic purposes. It works on the laws of reflection of sound.
Loudspeaker, Megaphone and bulb horn are devices used to send the sound in desired direction without spreading the sound all around. These devices act on the laws of reflection of sound wave.
Sound board is used to send the sound towards audience in big hall or auditorium. This works on the basis of laws of reflection of sound waves.

An echo is the repitition of the original sound heard after the sound is reflected from a distant,dense and rigid object.

When a number of echoes of the original sound are heard,each echo being fainter than the preceding one,such multiple echoes are called reververations.

SONAR (Sound Navigation and Ranging): Sonar is a device which is used to find the depth of the sea,or to locate underwater objects like enemy's submarine,sunken ships,shoal of fish,etc.

A sound board is a concave board (curved board) that is placed behind the speaker. The speaker is made to stand at the focus of the concave sound board. This setup solves the problem of interference of the sound waves with the large walls of the hall or auditorium.

The sound whose frequency lies between 20 Hz and 20000 Hz which we are able to hear is called audible sound.

Inaudible sounds having frequency less than 20 Hz are known as infrasonic sounds.

Inaudible sounds having frequecy more than 20000 Hz are known as ultrasonic sounds.

When a body is travelling at a speed greater than the speed of sound,we say that the body is travelling at a supersonic speed.

The eardrum is a stretched membranous structure at the junction of outer ear and middle ear. Vibration of eardrum causes production of sound that we hear. It is also known as tympanic membrane.