Wave Speed

Q. Earthquakes generate sound waves inside the earth. Unlike a gas, the earth can experience both transverse (S) and longitudinal (P) sound waves. Typically the speed of S wave is about 4.0 km s¯¹, and that of P wave is 8.0 km s–1. A seismograph records P and S waves from an earthquake. The first P wave arrives 4 min before the first S wave. Assuming the waves travel in straight line, at what distance does the earthquake occur ?

Q. Light can travel in vacuum but sound cannot because

1. speed of sound is very smaller than speed of light
2. light waves are electromagnetic in nature
3. sound waves are electromagnetic in nature
4. speed of light is very high

Q.

In the experiment for the determination of the speed of sound in air using the resonance column method, the length of the air column that resonates in the fundamental mode, with a tuning fork is 0.1 m. when this length is changed to 0.35 m, the same tuning fork resonates with the first overtone. Calculate the end correction

1. 0.05m

2. 0.024m

3. 0.025 m

4. 0.012 m

Q.

The wavelengths of $60cm$ and $61cm$, produce $9beats/sec$. The velocity of sound is (approximately)

1. $330m/s$

2. $335m/s$

3. $340m/s$

4. $325m/s$

Q.

The minimum audible wavelength at room temperature is about

[AFMC 1996]

1. 5 cm to 2 metre

2. 

3. 

4. 20 mm

Q.

The length of two open organ pipes are l and ( l + $\Delta l)$ respectively. Neglecting

end correction, the frequency of beats between them will be approximately

(Here v is the speed of sound)

[MP PET 1994; BHU 1995]

1. 

2. 

3. 

4. 

Q. A bat is flitting about in a cave, navigating via ultrasonic beeps. Assume that the sound emission frequency of the bat is 40 kHz. During one fast swoop directly toward a flat wall surface, the bat is moving at 0.03 times the speed of sound in air. What frequency does the bat hear reflected off the wall ?

Q. A sound wave of frequency $10\text{kHz}$ is travelling in air with speed of $340\text{m/s}$. Find the minimum separation between two points in the medium where the phase difference is $2\pi$.

1. $3.4\text{cm}$
2. $6.8\text{cm}$
3. $1.7\text{cm}$
4. $5.1\text{cm}$

Q. A tuning fork with a time period of $\frac{1}{256}\text{s}$ produces a sound wave in which the separation between adjacent compression and rarefaction is $0.7\text{m}$. Then, the speed of sound wave is

1. $250\text{m/s}$
2. $400\text{m/s}$
3. $310\text{m/s}$
4. $358\text{m/s}$

Q. A tuning fork is used to produce resonance in a glass tube. The length of the air column in this tube can be adjusted by a variable piston. At room temperture of ${27}^{o}C$, two successive resonances are produced at $20cm$ and $73cm$ of column length. If the frequency of the tuning fork is $320Hz$, the velocity of sound in air at ${27}^{o}C$ is approximately

1. $339m/s$
2. $330m/s$
3. $350m/s$
4. $300m/s$

Q. A hospital uses an ultrasonic scanner to locate tumours in a tissue. What is the wavelength of sound in the tissue in which the speed of sound is 1.7 km s¯¹ ? The operating frequency of the scanner is 4.2 MHz.

Q. Distance between successive compression and rarefaction in a sound wave is $1\text{m}$. If the velocity of sound is $360{\text{ms}}^{-1}$, find the frequency of sound wave.

1. $180\text{Hz}$
2. $160\text{Hz}$
3. $150\text{Hz}$
4. $120\text{Hz}$

Q. A steel rod 100 cm long is clamped at its middle. The fundamental frequency of longitudinal vibrations of the rod are given to be 2.53 kHz. What is the speed of sound in steel?

Q.

The equation of stationary wave along a stretched string is given by

y = 5 sin $\frac{\pi x}{3}cos40\pi t$ , where x and y are in cm and t in second. The

separation between two adjacent nodes is

[CPMT 1990; MP PET 1999; AMU 1999;

DPMT 2004; BHU 2005]

1. 1.5 cm

2. 3 cm

3. 6 cm

4. 4 cm

Q. The speed of longitudinal wave is given by $v=\sqrt{\frac{E}{\rho }}$ where $\rho$ is the density of the medium. Match the following columns for the quantities represented by $E$ in different media.
$\begin{array}{cccc}& \text{Column I}& & \text{Column II}\\ \text{(A)}& \text{Solid}& \text{(p)}& \text{Bulk modulus}\\ \text{(B)}& \text{Liquid}& \text{(q)}& \text{Shear modulus}\\ \text{(C)}& \text{Gas}& \text{(r)}& \text{Young's modulus}\end{array}$

1. $A\to p,B\to q,C\to r$
2. $A\to r,B\to q,C\to p$
3. $A\to r,B\to p,C\to q$
4. $A\to q,B\to r,C\to p$

Q. A sound wave of wavelength $4\text{mm}$ is produced in air, and it travels at a speed of $300\text{m/s}$. Will it be audible?

1. Yes
2. No
3. Sometimes audible & sometimes inaudible
4. Can't say

Q. Sound waves from a tuning fork A reach a point P by two separate paths ABP and ACP. When ACP is greater than ABP by 11.5cm, there is silence at P. When the difference is 23cm, the sound becomes loudest at P and when 34.5cm, there is silence again and so on. Calaulate the minimum frequency of the fork if the velocity of sound is taken to be 331.2m/s.

1. 0.23m, 1440 Hz
2. 0.46m, 1200 Hz
3. 0.23m, 1200 Hz
4. 0.46m, 1440 Hz

Q.

Aliens on the planet Xargon spot a distant dying star, 5 light years far. If we see the star dying today then after how much time will the star's explosion be heard by the Xargonians? (Assume Xargonians to be an immortal peace loving race) speed of sound $3\times {10}^2$ m/s

1. 5 light years

2. 10 years

3. 2000 years

4. Never ever

Q. A stone is dropped from the top of a tower of $500\text{m}$ height, into a pond of water at the base of the tower. When is the splash heard at the top?

$(\text{Given}g=10{\text{ms}}^{-2}$ and speed of sound $=340{\text{ms}}^{-1})$

1. $10\text{s}$
2. $11.47\text{s}$
3. $1.10\text{s}$
4. $20\text{s}$

Q. A sound wave of frequency $600\text{Hz}$ falls normally on a perfect reflecting wall. The minimum distance from the wall at which the particles of the medium will have maximum displacement during their vibrations is
[speed of sound $=300\text{m/s}$]

1. $\frac{7}{8}\text{m}$
2. $\frac{3}{8}\text{m}$
3. $\frac{1}{8}\text{m}$
4. $\frac{5}{8}\text{m}$

Q.

Aliens on the planet Xargon spot a distant dying star, 5 light years far. If we see the star dying today then after how much time will the star's explosion be heard by the Xargonians? (Assume Xargonians to be an immortal peace loving race) speed of sound $3\times {10}^2$ m/s

1. 5 light years

2. 10 years

3. 2000 years

4. Never ever

Q. A Kundt's tube apparatus has a copper rod of length $0.8\text{m}$ clamped at $40\text{cm}$ from one of the ends. The tube contains air in which the speed of sound is $330\text{m/s}$. The powder collected in the heaps are separated by a distance of $6\text{cm}$. What is the speed of sound wave in a copper rod?

1. $8.8\text{km/s}$
2. $3.4\text{km/s}$
3. $4.4\text{km/s}$
4. $6.8\text{km/s}$

Q. A sound wave travels a distance $l$ in helium gas in time $t$ at a particular temperature. If at the same temperature a sound wave is propagated in oxygen gas, it will cover the same distance $l$ in what time (approximately)?

1. $2t$
2. $4t$
3. $3t$
4. $5t$

Q. A sound wave is propagating through a medium following an adiabatic process . Imagine that after some time, it starts following an isothermal process. ($V_{iso}$ is the speed of sound when it follows isothermal process and $V_{ad}$ is the speed of sound when it follows adiabatic process). Then

1. $V_{ad}<V_{iso}$
2. $V_{ad}=V_{iso}$
3. $V_{ad}>V_{iso}$
4. None of these

Q.

Aliens on the planet Xargon spot a distant dying star, 5 light years far. If we see the star dying today then after how much time will the star's explosion be heard by the Xargonians? (Assume Xargonians to be an immortal peace loving race) speed of sound $3\times {10}^2$ m/s

1. 5 light years

2. 10 years

3. 2000 years

4. Never ever

Q. Sound waves from a tuning fork A reach a point P by two separate paths ABP and ACP. When ACP is greater than ABP by 11.5cm, there is silence at P. When the difference is 23cm, the sound becomes loudest at P and when 34.5cm, there is silence again and so on. Calaulate the minimum frequency of the fork if the velocity of sound is taken to be 331.2m/s.

1. 0.23m, 1440 Hz
2. 0.46m, 1200 Hz
3. 0.23m, 1200 Hz
4. 0.46m, 1440 Hz

Q. The relation between speed of sound in moist air $v_m$ and dry air $v_d$ at the same temperature and pressure will be

1. $v_m<v_d$
2. $v_m>v_d$
3. $v_m=v_d$
4. $v_m\le v_d$

Q. The speed of sound in hydrogen gas at $\text{STP}$ is $v_o$. The speed of sound in a mixture containing $3$ parts of hydrogen gas and $2$ parts of oxygen gas at $\text{STP}$ will be

1. $\frac{v_o}{\sqrt{3}}$
2. $\frac{v_o}{\sqrt{5}}$
3. $\frac{v_o}{\sqrt{6}}$
4. $\frac{v_o}{\sqrt{7}}$

Q.

Sound waves of wavelength $\lambda$ traveling in a medium with a speed of $vm{s}^{-1}$ enter in another medium, where its speed is $2vm{s}^{-1}$. What will be the wavelength of sound waves in the second medium?

1. $\lambda$

2. $4\lambda$

3. $2\lambda$

4. $3\lambda$

Q. The velocity of sound in hydrogen is $1400m{s}^{-1}$. What will be the velocity of sound in a mixture of gases having two parts by volume of hydrogen and one part by volume of oxygen. Maintaing the same pressure?

1. 371.4 m/s
2. 471.4 m/s
3. 571.4 m/s
4. 671.4 m/s