A source of unknown frequency gives 4 beats/s when sounded with a source of known frequency 250 Hz. The second harmonic of the source of unknown frequency gives five beats per second when sounded with a source of frequency 513 Hz. The unknown frequency is

1. 254 Hz

2. 246 Hz

3. 240 Hz

4. 260 Hz

Two sources of sound placed close to each other, are emitting progressive waves given by

${\mathrm{y}}_1$=4 sin 600$\mathrm{\pi t}$ and ${\mathrm{y}}_2$=5 sin 608 $\mathrm{\pi t}$

An observer located near these two sources of sound will hear

1. 4 beats per second with intensity ratio 25:16 between waxing and waning

2. 8 beats per second with intensity ratio 25:16 between waxing and waning

3. 8 beats per second with intensity ratio 81:1 between waxing and waning

4. 4 beats per second with intensity ratio 81:1 waxing and waning

Each of the two strings of length 51.6 cm and 49.1 cm are tensioned separately by 20N force. Mass per unit length of both the strings is same and equal to 1 $g{m}^{-1}$When both the strings vibrate simultaneously the number of beats is :

1. 5                                                   

2. 7

3. 8                                                   

4. 3

Two waves of frequencies 20 Hz and 30 Hz travel out from a common point. The phase difference between them after 0.6 sec is :

(1) Zero

(2) $\frac{\pi }{2}$

(3) π

(4) $\frac{3\pi }{4}$

Two tuning forks when sounded together produced 4 beats/sec. The frequency of one fork is 256 Hz. The number of beats heard increases when the fork of frequency 256 Hz is loaded with wax. The frequency of the other fork is(in Hz) :

(1) 504

(2) 520

(3) 260

(4) 252

A tuning fork sounded together with a tuning fork of frequency 256 Hz emits two beats. On loading the tuning fork of frequency 256 Hz with wax, the number of beats heard are 1 per second. The frequency of the other tuning fork is :

(1) 257

(2) 258

(3) 256

(4) 254

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 :

(1) 250

(2) 252

(3) 260

(4) 262