Intuition of Beats

Q. A whistle producing sound waves of frequency 9500Hz is approaching a stationary person with speed v m per second .the velocity of sound is 300m per s .if the person can hear frequencies upto a max of 10000 Hz the max value of v upto which he can hear is
ans 15m per second

Q.

Can two different bulbs similar in all respects act as coherent sources?

Q. A sound wave of frequency 330 hertz is incident normally at reflected wall then minimum distance from wall at which particle vibrate very much? (velocity sound is 330 metre per second)

Q. To increase the frequency by $20\%$, the tension in the string vibrating on a Sonometer has to be increased by

1. $44\%$
2. $33\%$
3. $22\%$
4. $11\%$

Q. A tuning fork of frequency 380 Hz is moving towards a wall with a velocity of 4 m/s. Then the number of beats heard by a stationary listener between direct and reflected sounds will be (velocity of sound in air is 340 m/s)

1. 10
2. 0
3. 5
4. 7

Q. 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 cm. Find the frequency of sound if the speed of sound in air is 340 m s⁻¹.

Q.

Which of the options correctly represent one Beat?

1. A-E
2. B-D
3. B-E

4. C-E

Q. A mass $m$ is suspended from a spring. Its frequency of oscillation is $f$. The spring is cut into equal halves and the same mass is suspended from one of the two pieces of the spring. The frequency of oscillation is the mass will be

1. $\sqrt{2}f$
2. $2f$
3. $f/2$
4. $f$

Q. The tension of a stretched string is increased by $69\%$. In order to keep its frequency of vibration constant, its length must be increased by:

1. $30\%$
2. $20\%$
3. $69\%$
4. $\sqrt{69}\%$

Q. A massless rod is suspended by two identical strings $AB$ and $CD$ of equal length. A block of mass $m$ is suspended from point $O$ such that $BO$ is equal to '$x$'. Further, it is observed that the frequency of 1st harmonic (fundamental frequency) in $AB$ is equal to 2nd harmonic frequency in $CD$. Then, length of $BO$ is :

1. $4L/5$
2. $L/5$
3. $3L/4$
4. $L/4$

Q. A wire having a linear density 0.10 kg/m is kept under a tension 490 N it is observed that it resonates at a frequency of 400 Hz and the next frequency 450 Hz. The length of the wire is

1. 14 m
2. 1.6 m
3. 0.7 m
4. 0.49 m

Q. A tuning fork of known frequency 256 Hz makes 5 beats per second with the vibrating string of a piano. The beat frequency decreases to 2 beats per second when the tension in the piano string is slightly increased. The frequency of the piano string before increasing the tension was :

1. (256 + 2) Hz
2. (256 - 2) Hz
3. (256 + 5) Hz
4. (256 - 5) Hz

Q. $41$ forks are so arranged rthat each produces $5$ beats per sec when sounded with its near fork . If the frequency of last fork is double the frequency of first fork, then the frequency if the first and last fork are respectively

1. $200,400$
2. $205,410$
3. $195,390$
4. $100,200$

Q. A sonometer wire 110 cm long produces a resonance with a tuning fork. When its length is decreased by 10 cm, 9 beats per second are heard. The frequency of tuning fork is __________.

1. $85$ Hz
2. $75$ Hz
3. $82$ Hz
4. $90$ Hz

Q. A light pointer fixed to one prong of a tuning fork touched a vertical plate. The fork is set vibrating and plate is allowed to fall freely. $8$ complete oscillations are counted when the plate falls through $10cm$. What is the frequency of the tuning fork?

1. $40\sqrt{2}$
2. $40\sqrt{3}$
3. $20\sqrt{2}$
4. $70\sqrt{2}$

Q. Find frequency of mass in the setup shown below, when displaced from its equilibrium position.

1. $\sqrt{\frac{3k}{m}}$
2. $\sqrt{\frac{k}{m}}$
3. $\sqrt{\frac{2k}{m}}$
4. $\sqrt{\frac{m}{3k}}$

Q. Two identical wires are stretched by the same tension of 100 N and each emits a note of frequency 200 Hz. If the tension in one wire is increased by 1 N, then the beat frequency is

1. $2Hz$
2. $1Hz$
3. $None$
4. $\frac{1}{2}Hz$

Q. Two wires are in unison. if the tension in one of the wires is increased by 2% , 5 beats are produced per second. the initial frequency of each wire is

1. 200Hz
2. 400Hz
3. 500Hz
4. 1000Hz

Q. Assertion :In spring block system if length of spring and mass of block both are halved, then angular frequency of oscillations will remain unchanged Reason: Angular frequency is given by $\omega =\sqrt{\frac{k}{m}}$.

1. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
2. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
3. Assertion is correct but Reason is incorrect
4. Assertion is incorrect but Reason is correct

Q. Two oscillators are started simultaneously in same phase. After $50$ oscillations of one, they get out of phase by $\pi$, that is half oscillation. The percentage difference of frequencies of the two oscillators is nearest to:

1. $2\text{\%}$
2. $0.5\text{\%}$
3. $0.25\text{\%}$
4. $1\text{\%}$

Q. Two identical straight wires are stretched so as to produce 6 beats per second when vibrating simultaneously. On changing the tension slightly in one of them, the beats frequency remains unchanged. Denoting by $T_1,T_2$ the higher and the lower initial tensions in the strings $(T_1>T_2)$, then it could be said that while making the above changes in tension

1. $T_1$ was decreased or $T_2$ was increased
2. $T_1$ was increased or $T_2$ decreased
3. $T_1$ was increased or $T_2$ increased
4. $T_1$ was decreased or $T_2$ decreased

Q.

Two identical straight wires are stretched so as to produce 6 beats per second when vibrating simultaneously. On changing the tension slightly in one of them, the beat frequency remains unchanged. Denoting the higher and the lower initial tension in the strings as T₁, T₂ respectively, then it could be said that while making the above changes in tension :

1. $T_2$ was decreased

2. $T_1$ , $T_2$ remain the same

3. $T_1$ was decreased

4. $T_1$ increased

Q. Assertion :Two pure tones with different frequencies sounded at once will create the phenomenon known as beats. Reason: If the beats are slow enough, you should be able to hear a variation in intensity.

1. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
2. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
3. Assertion is correct but Reason is incorrect
4. Both Assertion and Reason are incorrect

Q.

Which of the options correctly represent one Beat?

1. A-E
2. B-D
3. B-E

4. C-E

Q. In the figure shown, a mass $m$ hangs by a string attached to mass $M$.
What is the frequency of oscillation ?

Q. Two vibrating strings of the same material but lengths $L$ and $2L$ have radii $2r$ and $r$ respectively. They are stretched under the same tension. Both the strings vibrate in their fundamental modes, the one of length $L$ with frequency $v_1$ and the other with frequency $v_2$ . The ratio $\frac{v_1}{v_2}$ is given by

1. $4$
2. $2$
3. $8$
4. $1$

Q. A tuning fork A produces 4 beats/s with another tuning fork of frequency 320 Hz. On filling the fork A, 4 beats/s are again heard. The frequency of fork A, before filling is :

1. 318
2. 316
3. 320
4. 312

Q. Two identical piano wires have a fundamental frequency of $60vib/sec$. when kept under the same tension. What fractional increase in the tension of one wire will lead to the occurrence of six beats per second when both wires vibrate simultaneously.

Q.

Two identical straight wires are stretched so as to produce 6 beats per second when vibrating simultaneously. On changing the tension slightly in one of them, the beat frequency remains unchanged. Denoting the higher and the lower initial tension in the strings as T₁, T₂ respectively, then it could be said that while making the above changes in tension :

1. T₂ was decreased

2. T₁ was decreased

3. T_{1 ,} T₂ remain the same

4. T₁increased

Q. A closed organ pipe and an open organ pipe of the same length produce 4 beats when they are set into vibrations simultaneously. If the length of each of them were twice their initial lengths, the number of beats produced will be

1. 2
2. 4
3. 8
4. 1