Explanation
For the passengers in train A, there is no relative motion between source and observer, as both are moving with velocity 20 m/s. Therefore, there is no change in observed frequencies and correspondingly there is no change in their intensities, Therefore, the correct option is (a).
Sound waves require material medium to travel. As there is no atmosphere (vacuum) on the surface of moon, therefore the sound waves cannot reach from one person to another.
Transverse waves travel in the form of crests and troughs involving change in shape of the medium. As liquids and gases do not possess the rigidity therefore, transverse waves cannot be produced in liquid and gases. Also light wave is one example of transverse wave.
Sound waves cannot propagate through vacuum because sound waves arc mechanical waves. Light waves can propagate through vacuum because light waves are electromagnetic waves.. Since sound waves arc longitudinal waves, the particles moves in the direction of propagation, therefore these waves cannot be polarised.
Since transverse wave can propagate through medium which posses elasticity of shape. Air posses only volume elasticity therefore transverse wave cannot propagate through air.
According to Laplace, the changes in pressure and volume of a gas, when sound waves propagated through it, arc not isothermal, but adiabatic. A gas is a bad conductor of heat. It does not allow the free exchange of heat between compressed layer, rarefied layer and surrounding.
The velocity of every oscillating particle of the medium is different at its different positions in one oscillation but the velocity of wave motion is always constant i.e., particle velocity vary with respect to time, while the wave velocity is independent of time.
Also for wave propagation medium must have the properties of elasticity and inertia.
Speed of light is greater than that of sound, hence flash of lightening is seen before the sound of thunder.
A tuning fork is made of a material for which elasticity does not change. Since the alloy of nickel, steel and chromium (elinvar) has constant elasticity, therefore it is used for the preparation of tuning fork.
For the propagation of transverse waves, medium must have the property of rigidity. Because gases have no rigidity, (they do not possess shear elasticity), hence transverse waves cannot be produced in gases. On the other hand, the solids possess both volume and shear elasticity and likewise both the longitudinal and transverse waves can be transmitted through them.
When moisture is present in air, the density of air decreases. It is because the density of water vapours is less than that of dry air. The velocity of sound is inversely proportional to the square root of density, hence sound travel faster in moist air than in the dry air. Therefore, on a rainy day sound travels faster than on a dry day.
Sound produced by an open organ pipe is richer because it contains all harmonics and frequency of fundamental note in an open organ pipe is twice the fundamental frequency in a closed organ pipe of same length.
Reason is also correct, but it is not explaining the assertion.
Since the initial phase difference between the two waves coming from different violins changes, therefore, the waves produced by two different violins does not interfere because two waves interfere only when the phase difference between them remain constant throughout.
The person will hear the loud sound at nodes than at antinodes. We know that at antinodes the displacement is maximum and pressure change is minimum while at nodes the displacement is zero and pressure change is maximum. The sound is heard due to variation of pressure. Also in stationary waves particles in two different segment vibrates in opposite phase.
The principle of superposition does nor state that the frequencies of the oscillation should be nearly equal. For beats to be heard the condition is that difference in frequencies of the two oscillations should not he more than 10 times per seconds for a normal human ear to recognise it. Hence we cannot hear beats in the case of two tuning forks vibrating at frequencies 256 Hz and 512 Hz respectively.
Since there is no relative motion between the source and listener, So apparent frequency equals original frequency.
In open organ pipe 3rd overtone corresponds to 4th harmonic mode.
Also in open pipe, Number of nodes = Order of mode of vibration and number of antinodes = (Number of nodes + 1). Here number of nodes = 4, Number of antinodes = 4 + 1= 5.
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