Waves Questions and Answers Part-20

1.Two adjacent piano keys are struck simultaneously. The notes emitted by them have frequencies \[n_{1}\]  and \[n_{2}\]  . The number of beats heard per second is
a) \[\frac{1}{2}\left(n_{1}- n_{2}\right)\]
b) \[\frac{1}{2}\left(n_{1}+ n_{2}\right)\]
c) \[n_{1}\sim n_{2}\]
d) \[2\left(n_{1}- n_{2}\right)\]

Answer: c
Explanation: \[n_{1}\sim n_{2}\]

2. A tuning fork of frequency 100 when sounded together with another tuning fork of unknown frequency produces 2 beats per second. On loading the tuning fork whose frequency is not known and sounded together with a tuning fork of frequency 100 produces one beat, then the frequency of the other tuning fork is
a) 102
b) 98
c) 99
d) 101

Answer: a
Explanation:
q192
q192a

3.A tuning fork sounded together with a tuning fork of frequency 256 emits two beats. On loading the tuning fork of frequency 256, the number of beats heard are 1 per second. The frequency of tuning fork is
a) 257
b) 258
c) 256
d) 254

Answer: d
Explanation:
q193

4. If two tuning forks A and B are sounded together, they produce 4 beats per second. A is then slightly loaded with wax, they produce 2 beats when sounded again. The frequency of A is 256. The frequency of B will be
a) 250
b) 252
c) 260
d) 262

Answer: b
Explanation:
q194

5. The frequencies of two sound sources are 256 Hz and 260 Hz. At t = 0, the intensity of sound is maximum. Then the phase difference at the time t = 1/16 sec will be
a) Zero
b) \[\pi\]
c) \[\pi/2\]
d) \[\pi/4\]

Answer: c
Explanation: Time interval between two consecutive beats
q195

6. Two tuning forks have frequencies 450 Hz and 454 Hz respectively. On sounding these forks together, the time interval between successive maximum intensities will be
a) 1/4 sec
b) 1/2 sec
c) 1 sec
d) 2 sec

Answer: a
Explanation:
q196

7. When a tuning fork of frequency 341 is sounded with another tuning fork, six beats per second are heard. When the second tuning fork is loaded with wax and sounded with the first tuning fork, the number of beats is two per second. The natural frequency of the second tuning fork is
a) 334
b) 339
c) 343
d) 347

Answer: d
Explanation:
q197

8.Two tuning forks of frequencies 256 and 258 vibrations/sec are sounded together, then time interval between consecutive maxima heard by the observer is
a) 2 sec
b) 0.5 sec
c) 250 sec
d) 252 sec

Answer: b
Explanation:
q198

9.A tuning fork gives 5 beats with another tuning fork of frequency 100 Hz. When the first tuning fork is loaded with wax, then the number of beats remains unchanged, then what will be the frequency of the first tuning fork
a) 95 Hz
b) 100 Hz
c) 105 Hz
d) 110 Hz

Answer: c
Explanation:
q199
q199a

10.Tuning fork \[F_{1}\]  has a frequency of 256 Hz and it is observed to produce 6 beats/second with another tuning fork \[F_{2}\]  . When \[F_{2}\]  is loaded with wax, it still produces 6 beats/second with \[F_{1}\]  . The frequency of \[F_{2}\]  before loading was
a) 253 Hz
b) 262 Hz
c) 250 Hz
d) 259 Hz

Answer: b
Explanation:
q200