t 95~, A sour ce of unk now n freq uenc y give s 4 beat s/s,
I t I
whe n soun ded with a sour ce of kno wn freq uenc y
'
250 Hz, The seco nd harm onic of the sour ce of
I
unk now n freq uenc y give s five beat s per seco nd, whe n
sour ided with a sour ce of freq uenc y 513 Hz. The
unk now n freq uenc y is :,i:.ET · ~~
, (a) 254 Hz 1
(~) 246 Hz (c) 240 Hz (d) 260 Hz
96~ Two vibr ating tuni ng fork s prod uce wav es
give n by y1 =4si n50 0~t and y =2si n506 nt. Num ber
2
o( bea ~ prod u~ed per min ute is
(a) 360 (b) 180 (c) 60 (d) 3 [PMT 06J
9r7. Two sour ces of sotm d plac ed close to each
othe r are emit ting prog ress ive wav es give n I by
y 1, :; 4SA'\6001tt and y2 = ~sin6o81tt. An obse rver loca ted
':'E:~~ ,th~se ~Q· sour ces of soun d will rear I
(a) 4 1beat s per seco nd with ihten sity ratio 25: 16
betw een wax ing and wan ing
(b) 8 beat s per seco nd with inten sity ratio •2s : 16
betw een wax ing and wan ing
1
(c) 8 bec\ts per se~ond with intensity ratio 81 : 1
t betw een wax ing and wan ing
(d) 4 beat s per second with intensity ratio 81 : 1
betw een wax ing and wan ing. [AIP ~ Pre 121
98. Thre e soun d wav es of equa l amp litud es have
frequencies ( n -1 ~ n, ( n + 1). They supe rimp ose to give
beat s. The num ber of beats prod uced per seco nd will be
(a) 3 (b) 2 (c) 1 (d) 4 [NEET'lll
