Physics · Science General

Acoustics and Sound Waves

2,160 Questions

Acoustics and sound waves deal with mechanical vibrations traveling through media like air and water. Key concepts include wave reflection, beats, echoes, the Mach number, and infrasound. These physics fundamentals are regularly tested in general science sections of multiple competitive exams.

Sound wave propagationEchoes and reflectionWave interferenceMach numberInfrasound frequency

Acoustics and Sound Waves Questions

Multiple choice physics propagation of sound waves longitudinal vs transverse wave sound and light comparison of speed of sound with speed of light

The ratio of speed of ultrasonic wave and sound wave is:

  1. $=1$
  2. $>1$
  3. $<1$
  4. $>1$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Ultrasonic wave is  defined as “inaudible sound with high frequency for human” the frequency of which generally exceeds 20 kHz. These days, sound wave which is not intended to be heard is also called Ultrasonic wave .


Ultrasonic wave is also a type of sound wave so ratio of velocity is $=1$

Multiple choice physics propagation of sound waves longitudinal vs transverse wave sound and light comparison of speed of sound with speed of light

The speed of sound is $330 ms^{-1}$ and that of light is $3\times 10^8 ms^{-1}$. The ratio of speed of sound to that of light is approximately $1 : 10^6$.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Speed Of Sound$(V)$  is,  $330m/s$  and  that of Light$(U)$  is,  $300*10^{6}m/s$

Now we have to find,  $V:U$  and i.e.,  $V:U=330:300*10^{6}\cong1:10^{6}$ , because in comparison to $U$(Speed of Light)  ,  Speed of Sound$(V)$  is comparetively very $small$.
So, we can assume that, Speed of Sound$(V)$  is $300m/s$  in comparison to that of Speed of Light$(U)$ that is  $3*10^{6}$
Hence,  $V:U=1:10^{6}$

Hence, it is True.
Option A is correct

Multiple choice physics propagation of sound waves longitudinal vs transverse wave sound and light comparison of speed of sound with speed of light

The correct statement is:

  1. Sound and light both require medium for propagation.

  2. Sound can travel in vacuum, but light can not.

  3. Sound needs medium, but light does not need medium for its propagation.

  4. Sound and light both can travel in vacuum.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Sound waves need to travel through a medium such as a solid, liquid, or gas. The sound waves move through each of these mediums by vibrating the molecules in the matter. The molecules in solids are packed very tightly. Liquids are not packed as tightly as solids. And gasses are very loosely packed. The spacing of the molecules enables sound to travel much faster through a solid than a gas. Sound travels about four times faster and farther in water than it does in air. 
Sound waves are traveling vibrations of particles in media such as air, water or metal. So it stands to reason that they cannot travel through empty space, where there are no atoms or molecules to vibrate.
Light travels as a wave. But unlike sound waves or water waves, it does not need any matter or material to carry its energy along. This means that light can travel through a vacuum, a completely airless space. Nothing travels faster than light energy. 
Hence, the statement "Sound needs medium, but light does not need medium for its propagation." is correct.

Multiple choice physics propagation of sound waves longitudinal vs transverse wave sound and light comparison of speed of sound with speed of light

The sound of lightning flash is heard $3$ second after the flash is seen. The distance of the lightning is $1020$ metre. The speed of sound is:

  1. $1400\ m/s$
  2. $332\ m/s$
  3. $340\ m/s$
  4. $none\ of\ these$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Given data,
Distance $d=1020 m$
Time $t=3s$
Speed$=?$
$Speed=\dfrac{distance }{time}=\dfrac{1020}{3}=340 m/s$

Multiple choice physics propagation of sound waves longitudinal vs transverse wave sound and light comparison of speed of sound with speed of light

The speed of sound in air is  330m/s. It takes 10s for sound to reach a certain distance from the source placed in air. Find the distance.

  1. 669m

  2. 330m

  3. 3300m

  4. 1200m
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

$\displaystyle V=330{ m }/{ s },t=2s,V=\frac { d }{ t } $
$\displaystyle d=V\times t$
$\displaystyle =330\times 10=3300m$

Multiple choice physics propagation of sound waves longitudinal vs transverse wave sound and light comparison of speed of sound with speed of light

On a hot, dry summer day a boy is standing between plane parallel vertical cliffs separated by $75m$. He is $30$m away from one of the cliffs. Consider speed of sound in air on that hot day to be $360m/s$. The boy claps loudly and hearts its successive echoes. The time in seconds at which he hears the first four echoes are respectively

  1. $\displaystyle \frac{1}{6}, \frac{1}{4}, \frac{5}{12}, \frac{5}{12}$
  2. $\displaystyle \frac{1}{6}, \frac{1}{4}, \frac{7}{12}, \frac{2}{3}$
  3. $\displaystyle \frac{1}{4}, \frac{1}{3}, \frac{5}{12}, \frac{5}{12}$
  4. $\displaystyle \frac{1}{6}, \frac{1}{4}, \frac{1}{3}, \frac{5}{12}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

First echo : When sound goes to the cliff 1 and returns to his ear

Distance traveled by sound, $S = 30+30 = 60$ m
Time taken, $t _1 = \dfrac{60}{360} = \dfrac{1}{6}$ s

Second echo : When sound goes to the cliff 2 and returns to his ear
Distance traveled by sound, $S = 45+45 = 90$ m
Time taken, $t _2 = \dfrac{90}{360} = \dfrac{1}{4}$ s

Third echo : When the reflected sound from cliff 1 goes to the cliff 2 and returns to his ear
Distance traveled by sound, $S = 30+75+45 = 150$ m
Time taken, $t _3 = \dfrac{150}{360} = \dfrac{5}{12}$ s

Fourth echo : When the reflected sound from cliff 2 goes to the cliff 1 and returns to his ear
Distance traveled by sound, $S = 45+75+30 = 150$ m
Time taken, $t _4 = \dfrac{150}{360} = \dfrac{5}{12}$ s

Multiple choice physics properties of waves longitudinal and transverse waves travelling waves types of waves

A metal hammer hits a spherical bell, when the circuit in a calling bell is switched ON, the propogation of sound takes place due to 

  1. Air

  2. electric current

  3. metal bell

  4. none of the above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Though the hammer strikes the bell and the bell starts vibrating, these vibrations are then carried out to the atmosphere only by air molecules thereby creating a sound

The correct option is (a)

Multiple choice physics properties of waves longitudinal and transverse waves travelling waves types of waves

Waves that are combination of longitudinal and transverse nature are

  1. water waves

  2. light waves

  3. shock waves

  4. sound waves
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Water waves are an example of waves that involve a combination of both longitudinal and transverse motions. As a wave travels through the waver, the particles travel in clockwise circles. The radius of the circles decreases as the depth into the water increases. The animation at right shows a water wave travelling from left to right in a region where the depth of the water is greater than the wavelength of the waves. I have identified two particles in orange to show that each particle indeed travels in a clockwise circle as the wave passes.

Multiple choice physics sound and noise musical sound and scale pleasant, unpleasant sounds and noise pollution sound noise and pollution

While travelling by train, when the train passes through the tunnel, why does our ear aches ?

  1. atmospheric pressure

  2. tunnel pressure

  3. water pressure

  4. None of the above

Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

When a train enters a tunnel, it compresses the air in front of it like a piston. Unlike outside air, air in a tunnel can’t be simply pushed aside—the tunnel walls are in the way. Some of the air is pushed forward, all the way down to the tunnel’s other end, but most of it rushes through the narrow space between the train and the tunnel walls, filling in the area behind the train. Being forced into this narrow space makes the air rush faster, exactly as water speeds up at the base of a funnel. In fact, this tunnel air can rush backward much faster than the train’s forward speed. his fast moving air creates a kind of suction on the train, lowering the air pressure inside and making your ears go pop. It cause ear aches

Hence, due to sudden increase and decrease pressure inside tunnel, aches occur in ear