Practice free Waves (Physics) NEET multiple-choice questions online with instant answers and detailed explanations. No login required.
A stationary wave of frequency 200 hz are formed in air. If the velocity of the wave is 360 m/s, the shortest distance between two antinodes is …….m
A tuning fork produces 8 beats per second with both 80 cm and 70 cm of stretched wire of a sonometer. Frequency of the fork is …….hz.
An open pipe is in resonance in 2nd harmonic with frequency f . Now one end of the tube is closed and frequency is increased to f2, such that the resonance again occurs in the nth harmonic. Choose the correct option.
When an open pipe is in resonance in its 2nd harmonic, the frequency is given by $f = rac{2v}{2L}$, where $L$ is the length of the pipe. If one end of the pipe is closed, the pipe behaves like a closed pipe, and the nth harmonic for a closed pipe is given by the odd harmonics (1, 3, 5, ...). For the pipe to resonate again, the frequency must be adjusted. For $n = 5$, the frequency $f_2$ would be $ rac{5v}{4L}$. Therefore, $f_2 = rac{5}{4} f$. Hence, the correct option is $n = 5, f_2 = (5 / 4) f_1$.
Assertion – Reason type questions : For the following questions, statement as well as the reason(s) are given. Each questions has four options. Select the correct option. Statement – 1: Two waves moving in a uniform string having uniform tension cannot have different velocities. Statement – 2 : Elastic and inertial properties of string are same for all waves in same string. Moreover speed of wave in a string depends on its elastic and inertial properties only.
Assertion – Reason type questions : For the following questions, statement as well as the reason(s) are given. Each questions has four options. Select the correct option. Statement – 1: When a sound source moves towards observer, then frequency of sound increases. Statement – 2 : Wavelength of sound in a medium moving towards the observer decreases.
Assertion – Reason type questions : For the following questions, statement as well as the reason(s) are given. Each questions has four options. Select the correct option. Statement – 1: Newton’s equation for speed of sound was found wrong because he assumed the process to be isothermal. Statement – 2 : When sound propagates, the compressions and rarefactions happen so rapidly that there is not enough time for heat to be distributed.
Newton initially assumed that the propagation of sound in air was an isothermal process (constant temperature). However, it was later found that the process is actually adiabatic (no heat exchange due to rapid compression and rarefaction). The rapid compressions and rarefactions in sound waves do not allow enough time for heat to be distributed, thus making the process adiabatic. Therefore, both statements are true, and statement 2 correctly explains why Newton's assumption was incorrect.
Assertion – Reason type questions : For the following questions, statement as well as the reason(s) are given. Each questions has four options. Select the correct option. Statement – 1 : When pressure in a gas changes, velocity of sound in gas may change. Statement – 2 : Velocity of sound is directly proportional to square root of pressure.
The velocity of sound in a gas is given by the formula \( v = \sqrt{\frac{\gamma P}{\rho}} \), where \( v \) is the velocity, \( \gamma \) is the adiabatic index, \( P \) is the pressure, and \( \rho \) is the density. When the pressure in a gas changes, the velocity of sound may change, but this change is not directly proportional to the square root of pressure alone; it also depends on the density of the gas. Hence, statement 1 is true, statement 2 is true, but statement 2 is not the correct explanation of statement 1.
Assertion – Reason type questions : For the following questions, statement as well as the reason(s) are given. Each questions has four options. Select the correct option. Statement – 1 : If wave enters from one medium to another medium then sum of amplitudes of reflected wave and transmitted wave is equal to the amplitude of incident wave. Statement – 2 : If wave enters from one medium to another medium some part of energy is transmitted and rest of the energy is reflected back.
A string 25 cm long and having a mass of 2.5 g is under tension. A pipe closed at one end is 40 cm long. When the string is set vibrating in its first overtone and the air in the pipe in its fundamental frequency, 8 beats per second is heard. It is observed that decreasing the tension in the string decreases the beat frequency. The speed of sound in air is $320 ms– 1$ The frequency of the string vibrating in its 1st overtone is …… hz
Since the beat frequency is 8, the frequency of the string vibrating in its first Overtone is 192 Hz or 208 Hz Where for 1st Overtone frequency $ f_1 = { 1 \over l } \sqrt { T \over m} ....(1) $ It is given that the beat frequency decreases if the tension in the string is decreased. $ \therefore f_1 ' \gt f_1$ Hence $f_1 ' = 208Hz and not 192Hz$
A string 25 cm long and having a mass of 2.5 g is under tension. A pipe closed at one end is 40 cm long. When the string is set vibrating in its first overtone and the air in the pipe in its fundamental frequency, 8 beats per second is heard. It is observed that decreasing the tension in the string decreases the beat frequency. The speed of sound in air is $320 ms– 1$ The tension in the string is very nearly equal to ……
substituting the values of l.m and $f_1 '$ in equation 1 we get T = 27.04 N
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