Waves practice · Mixed difficulty

A sonometer is set on the floor of a lift. When the lift is at rest, the sonometer wire vibrates with fundamental frequency 256 Hz. When the lift goes up with acceleration $a = \frac{{9g}}{{16}}$ vibration of the same wire changes to

In Quincke's experiment the sound detected is changed from a maximum to a minimum when the sliding tube is moved through a distance of $2.50 \mathrm{~cm}$. Find the frequency of sound if the speed of sound in air is $340 \mathrm{~ms}^{-1}$.

Assertion: If a vibrating tuning fork is held near the ear and given one full rotation, then intensity of sound becomes maximum four times and minimum two times.
Reason: A stationary wave transmits energy.

Which of the following statements are true for wave motion?

Assertion: In a medium group velocity is greater than phase velocity.
Reason: $\frac{dv}{d\lambda}$ is $+$ve.

A wave pulse in string is described by the equation ${y}_1=\frac{5}{(3 x-4 t)^2+2}$ and another wave pulse in the same string is described by ${y}_2=\frac{-5}{(3 x+4 t-6)^2+2}$. The values of ${y}_1, {y}_2$ and ${x}$ are in meters and ${t}$ is in seconds. Which of the following statement is correct?

If the speed of longitudinal waves is equal to 10 times the speed of the transverse waves in a stretched wire of material which has modulus of elasticity $E$, then the stress in the wire is

A string of length $0.4 \mathrm{~m}$ and mass $10^{-2} \mathrm{~kg}$ is clamped at its ends. The tension in the string is $1.6 \mathrm{~N}$. When a pulse travels along the string, the shape of the string is found to be the same at times $t$ and $t+\Delta t$. The value of $\Delta t$ is -

When a train is at a distance of $2 \mathrm{~km}$, its engine sounds a whistle. A man near the railway track hears the whistle directly and by placing his ear against the track of the train. If the two sounds are heard att an interval of $5.2 \mathrm{~s}$, the speed of the sound in iron (material of the rail track) is

(Given that velocity of sound in air is $330 \mathrm{~ms}^{-1}$)

The displacement $y$ of a particle in a medium can be expressed as $y = {10^{ - 6}}\,\,\sin \left( {100t + 20x + \frac{\pi }{4}} \right)m$, where $t$ is in second and $x$ in metre. The speed of the wave is

With propagation of longitudinal waves through a medium, the quantity transmitted is

A train moves towards a stationary observer with speed $34\,\,m{s^{ - 1}}$. The train sounds a whistle and its frequency registered by the observer is ${v_1}$. If the train’s speed is reduced to $17\,\,m{s^{ - 1}}$, the frequency registered is ${v_2}$. If the speed of sound is $340\,\,m{s^{ - 1}}$, then the ratio ${v_1}/{v_2}$ is

Four wires of identical length, diameters and of the same material are stretched on a sonometre wire. If the ratio of their tensions is $1\mathrm{ }:\mathrm{ }4\mathrm{ }:\mathrm{ }9\mathrm{ }:\mathrm{ }16$ then the ratio of their fundamental frequencies are

Assertion: Longitudinal waves are called pressure waves.
Reason: Propagation of longitudinal waves through a medium involves changes in pressure (density of medium particles), when compressions and rarefactions are formed.

Three resonant frequencies of string with both rigid ends are 90,150 and $210 \mathrm{~Hz}$. If the length of the string is $80 \mathrm{~cm}$, what is the speed of the transverse wave in the string?

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

A pulse of a wave train travels along a stretched string and reaches the fixed end of the string. It will be reflected with

Assertion: Explosions on other planets are not heard on earth.
Reason: To hear distinct beats difference infrequencies of two sources should be less than 10.

The source producing sound and an observer both are moving along the direction of propagation of sound waves. If the respective velocities of sound, source and an observer are $v, v_s$ and $v_o$, then the apparent frequency heard by the observer will be: ($n=$ frequency of sound)

Statement-I: In propagation of sound waves, pressure amplitude is proportional to the displacement amplitude.
Statement-II: Suppose the source and observer both are stationary and wind is blowing in a direction from source to observer, then the observer detects an apparent increase in frequency.

The equation of a wave on a string of linear mass density $0.04\,\,kg{m^{ - 1}}$ is given by $y = 0.02\left( m \right)\,\,\sin \left[ {2\pi \left( {\frac{t}{{0.04\left( s \right)}} - \frac{x}{{0.50\left( m \right)}}} \right)} \right]$. The tension in the string is

If the speed of a wave doubles as it passes from shallow water deeper water, its wavelength will be

In a stationary wave

Assertion: The change in air pressure affects the speed of sound.
Reason: The speed of sound in a gas is proportional to square root of pressure.

A motorcyclist going around a circular track of radius $50 \mathrm{~m}$ with a speed of $25 \mathrm{~m} / \mathrm{s}$, is at a point ${X}$. A static siren at ${Y}$ is emitting sound of frequency ${n}$. How many times (approximately) in an hour will the motor cyclist hear the sound of actual frequency ${Y}?$

Two aeroplanes $A$ and $B$ are approaching cach other and their velocities are $108 \mathrm{~km} \mathrm{~h}^{-1}$ and $144 \mathrm{~km} \mathrm{~h}^{-1}$ respectively. The frequency of a note emitted by $A$ as heard by the passengers in $B$ is $1170 \mathrm{~Hz}$. Calculate the frequency of the note heard by the passenger in A. Velocity of sound $=350 \mathrm{~ms}^{-1}$.

The beats are the examples of

The amplitude of a wave is given by $A$ $= \frac{c}{{a + b + c}}$ . Resonance will occur when

Two organ (open) pipes of length 50 cm and 51 cm produce ‘6’ beats/s. Then the speed of sound is nearly

Two sound sources emit the sounds of same frequency $f$. An observer is at the mid-way between the sources on the line joining them. When he starts moving towards one source with speed ${v} / 20$, where ' $v$ ' is speed of sound, he hears 10 beats per second. The value of ' ${f}$ ' is