Effect of Temperature, Pressure and Humidity

Q.

Use the formula $v=\sqrt{\frac{\gamma P}{\rho }}$ to explain why the speed of sound in air is independent of pressure, increases with temperature, increases with humidity.

Q. Speed of sound in air is $332\text{m/s}$ at NTP. What will be the speed of sound in hydrogen at NTP if the density of hydrogen at NTP is $\left(1/16\right)$ that of air?

1. $664\text{m/s}$
2. $166\text{m/s}$
3. $1155\text{m/s}$
4. $1328\text{m/s}$

Q. At room temperature, the velocity of sound in $O_2$ gas is $v$. Then, in a mixture of $H_2$ and $O_2$ gas, the speed of sound at the same temperature is

1. less than $v$.
2. nothing can be said.
3. more than $v$.
4. equal to $v$.

Q. Calculate the ratio of the speed of sound in neon to that in water vapour at any given temperature.
[molecular weight of neon $=2.02\times {10}^{-2}\text{kg/mol}$ and of water vapour $=1.8\times {10}^{-2}\text{kg/mol}$. Given that water vapour is triatomic]

1. $1.023$
2. $1.055$
3. $1.5$
4. $1.8$

Q. The velocities of sound at the same pressure in two monoatomic gases of densities ${\rho }_1$ and ${\rho }_2$ are $v_1$ and $v_2$ respectively. If $\frac{{\rho }_1}{{\rho }_2}=4$, then the value of $\frac{v_1}{v_2}$ is:

1. $\frac{1}{4}$
2. $\frac{1}{2}$
3. 2
4. 4

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 temperature of 27 degree C two successive resonances are produced at 20 cm and 73 cm column length. If the frequency of the tuning fork is 320 Hz, the velocity of sound in air at 27 degree C is

1. 330 m/s

2. 339 m/s

3. 350 m/s

4. 300 m/s

Q. A sound wave is produced in water and moves towards the surface of water and part of it moves in air. The velocity of sound in water is $1450\text{m/s}$ and that in air is $330\text{m/s}$. Which of the following statements is correct regarding the frequency $\left(f\right)$ and wavelength $\left(\lambda \right)$ of sound when it travels from water to air?

1. $f$ and $\lambda$ will remain same.
2. $f$ will remain the same but $\lambda$ will increase.
3. $f$ will remain the same but $\lambda$ will decrease.
4. $f$ will increase and $\lambda$ will decrease.

Q. Speed of sound in air at constant temperature

1. is proportional to the atmospheric pressure.
2. is proportional to the square of atmospheric pressure.
3. is proportional to the square root of atmospheric pressure
4. does not depend on atmospheric pressure.

Q.

At what temperature will the speed of sound in hydrogen be the same as in oxygen at ${100}^0$ C? Molar masses of oxygen and hydrogen are in the ratio 16:1.

1. $-{257}^{0}C$

2. $-{57}^{0}C$

3. $-{17}^{0}C$

4. $-{249.7}^{0}C$

Q.

What is the effect of increase of pressure on speed of sound in air.

Q.

The extension in a string obeying Hookes law is $x$. The speed of sound in the stretched string is $v$. If the extension in the string is increased to $1.5x$, the speed of sound will be

1. $1.22v$

2. $0.61v$

3. $1.50v$

4. $0.75v$

Q. The Doppler effect is applicable for

1. Light waves only
2. Sound waves only
3. Both light and sound waves
4. None of the above

Q.

The ratio of densities of nitrogen and oxygen is 14:16. The temperature at which the speed of sound in nitrogen will be same as that in oxygen at ${55}^{\circ }C$ is

1. 35°C

2. 48°C

3. 65°C

4. 14°C

Q.

Find the change in the volume of 1.0 litre kerosene when it is subjected to an extra pressure of $2.0\times {10}^{5}N{m}^{-2}$ from the following data. Density of kerosene $=800kg{m}^{-3}$ and speed of sound in kerosene = $1330m{s}^{-1}$.

Q. If at same temperature and pressure, the densities for two diatomic gases are $d_{1}and{d}_2$ respectively, then the ratio of velocities of sound in these gases will be

1. $d_1{d}_2$
2. $\sqrt{\left(d_1{d}_2\right)}$
3. $\sqrt{\left(\frac{d_2}{d_1}\right)}$
4. $\sqrt{\left(\frac{d_1}{d_2}\right)}$

Q. How long will it take sound waves to travel the distance between the points A and B, separated by a distance l, if the air temperature between them varies linearly from $T_1$ to $T_2$? The velocity of sound propagation in air is equal to $v=\alpha \sqrt{T}$
Where $\alpha$ is a constant.

1. $t=\frac{2l\alpha }{(\sqrt{T_2}+\sqrt{T_1})}$
2. $t=\frac{2\alpha }{l(\sqrt{T_2}+\sqrt{T_1})}$
3. $t=\frac{2l}{\alpha (T_2+T_1)}$
4. $t=\frac{2l}{\alpha (\sqrt{T_2}+\sqrt{T_1})}$

Q.

On a winter day sound travels 336 meters in one second. Find the atmospheric temperature. Speed of sound at 0${}^{\circ }$ C = 332 m s${}^{-1}$.

1. 7${}^{\circ }$C.

2. 14${}^{\circ }$C.

3. 0${}^{\circ }$C.

4. None of these

Q.

A submerged scuba diver hears the sound of a boat horn directly above her on the surface of the lake. At the same time, a friend on dry land 22.0 m from the boat also hears the horn (fig). The horn is 1.2 m above the surface of the water. What is the distance (labeled by "?” in fig) from the horn to the diver? Both air and water are at 20${}^{\circ }$C.

$B_{water}=2.2\times 109Pa,{\gamma }_{air}=1.4,M_{air}\approx 30g$

1. 90.5 m

2. 50 m

3. 10 m

4. None of these

Q. Calculate the difference in the speeds of sound in air at -3⁰C, 60cm pressure of mercury and 30⁰C, 75cm pressure of mercury. the speed of sound in air at 0⁰C is 332ms^-1.

Q. When you speak to you friend, which of the following parameters have a unique value in the sound produced?

1. Wave velocity

2. Frequency

3. Wavelength

4. Amplitude

Q.

Speed of sound in air is found to be 344$\frac{m}{s}$ at 80${}^{\circ }$ C. Find the change in speed of sound for a 1${}^{\circ }$ C increase in temperature.

1. None of these

2. 1 m/s

3. 0.6 m/s

4. 0.01 m/s

Q.

The bulk modulus and the density of water are greater than those of air. With this much of information, we can say that velocity of sound in air

1. cannot be compared with its value in water

2. Is larger than its value in water

3. Is smaller than its value in water

4. Is equal to its value in water

Q. A tuning fork sends sound waves in air. If the temperature of the air increases, which of the following parameters will change?

1. Displacement amplitude
2. Wavelength
3. Time period
4. Frequency

Q.

When two waves are mutually coherent it means that

Q.

The speed of sound as measured by a student in the laboratory on a winter day is 340 m s${}^{-1}$ when the room temperature is 17${}^{\circ }$ C. What speed will be measured by another student repeating the experiment on a day when the room temperature is 32${}^{\circ }$ C?

1. None of these

2. 333 m/s

3. 340 m/s

4. 350 m/s

Q. In sports, the timing of a 200 m straight dash is recorded at the finish point on hearing the sound of a gun fired at the starting point. The time recorded will be more accurate

1. in winter
2. in summer
3. in all seasons
4. none of these

Q.

The absolute temperature of air in a region linearly increases from $T_1$ to $T_2$ in a space of width d. Find the time taken by a sound wave to go through the region in terms of $T_1,T_2,d$ and the speed v of sound at 273 K.

1. None of these

2. 

3. 

4. 

Q. The difference in the speeds of sound in air at $-5^{\circ }C,$ 60 cm pressure of mercury and ${30}^{\circ }C,$ 75 cm pressure of mercury is (velocity of sound in air at $0^{\circ }C$ is 332 m/s)

1. 3.05 m/s
2. 15.25 m/s
3. 21.35 m/s
4. 18.3 m/s

Q. The ratio of velocity of sound in air at 4 atmosphere and that at 1 atmosphere pressure would be

1. 1 : 4
2. 3 : 1
3. 4 : 1
4. 1 : 1

Q. Which of the following statement is incorrect?

1. Change in pressure have no effect on the speed of sound
2. The speed of sound in water is higher than in air
3. Changes in temperature have no effect on the speed of sound
4. Frequency of sound wave does not change while travelling in different medium