Tag: sound waves are longitudinal waves

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Multiple choice physics world of sounds characteristics of sound wave time period, frequency and amplitude of sound sound waves are longitudinal waves

The velocity of sound in air is not affected by change in 

  1. the moisture content of the air.

  2. the temperature of air.

  3. the atmospheric pressure.

  4. the composition of air.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The speed of sound depends on temperature. The formula relating speed of sound and temperature is as follows:

$v = 331 + 0.6 \times T$, where $T$ is temperature in absolute scale and $v$ is in $m/s$.
Humidity has little effect on the speed of sound.
Air pressure has no effect at all in an ideal gas approximation. This is because pressure and density both contribute to sound velocity equally, and in an ideal gas the two effects cancel out each other, leaving only the effect of temperature.
Composition of air has also almost no effect on the speed of sound.

Multiple choice physics world of sounds characteristics of sound wave time period, frequency and amplitude of sound sound waves are longitudinal waves

Consider the following
l. Waves created on the surfaces of a water pond by a vibrating source.
ll. Wave created by an oscillating electric field in air.
lll. Sound waves travelling under water. 
Which of these can be polarized

  1. l and ll

  2. ll only

  3. ll and lll

  4. l, ll, and lll
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Sound waves are longitude and can not be polarized. Answer A

Multiple choice physics study of sound types of waves sound as a wave of disturbance sound waves are longitudinal waves

The longitudinal wave can be observed in

  1. Elastic media

  2. inelastic media
  3. Both $(1)$ & $(2)$

  4. None of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Longitudinal waves travel only in the elastic medium. These waves comprise of compressions and rarefactions. The speed of Longitudinal waves is given by :

$v=\dfrac{\sqrt{B}}{\rho }$ where B is the bulk modulus of elasticity and $\rho $ is the density of the medium

Multiple choice physics study of sound types of waves sound as a wave of disturbance sound waves are longitudinal waves

A transverse wave along a string is given by y=$2\sin \left( {2\pi \left( {3t - x} \right) - \frac{\pi }{6}} \right)$, where x and y are in cm and 't' is in second. The acceleration of a particle located at x=4cm at t =1s is 

  1. $36\pi ^2$
  2. $72\pi ^2$
  3. $18\pi ^2$
  4. $12\pi ^2$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The wave equation is y = 2 sin(6*pi*t - 2*pi*x - pi/6). Velocity v = dy/dt = 2 * 6*pi * cos(6*pi*t - 2*pi*x - pi/6). Acceleration a = dv/dt = -2 * (6*pi)^2 * sin(6*pi*t - 2*pi*x - pi/6). At x=4 and t=1, the argument is 6*pi - 8*pi - pi/6 = -2*pi - pi/6. sin(-2*pi - pi/6) = sin(-pi/6) = -1/2. Thus, a = -2 * 36*pi^2 * (-1/2) = 36*pi^2.

Multiple choice physics study of sound types of waves sound as a wave of disturbance sound waves are longitudinal waves

When a sound wave goes from one medium to another , the quantity that remains unchanged is

  1. Frequency

  2. amplitude

  3. wavelength

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

The electric and magnetic fields have to remain continuous at the refractive index boundary. If the frequency changed, the light at each side of the boundary would be continuously changing it's relative phase and there would be no way to match the fields.
Furthermore, for conservation of energy frequency should remain same.
Energy $E' = h\nu'$ inside the glass must be equal to the energy outside, so
$E = E'$ gives
$h\nu = h\nu'$
so $\nu = \nu'$
the frequency in the medium is equal to that of outside.
Ans: A

Multiple choice physics study of sound types of waves sound as a wave of disturbance sound waves are longitudinal waves
State whether the given statement is True or False :
Sound waves are transverse whereas light waves are longitudinal in nature in air.

  1. True

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

Sound is a mechanical wave that results from the back and forth vibration of the particles of the medium through which the sound wave is moving. If a sound wave is moving from left to right through air, then particles of air will be displaced both rightward and leftward as the energy of the sound wave passes through it. The motion of the particles is parallel to the direction of the energy transport. This is what characterizes sound waves in air as longitudinal waves.
Hence, the statement is false.