1
JEE Main 2019 (Online) 12th April Evening Slot
+4
-1
Two sources of sound S1 and S2 produce sound waves of same frequency 660 Hz. A listener is moving from source S1 towards S2 with a constant speed u m/s and he hears 10 beats/s. The velocity of sound is 330 m/s. Then, u equals :
A
10.0 m/s
B
5.5 m/s
C
15.0 m/s
D
2.5 m/s
2
JEE Main 2019 (Online) 12th April Evening Slot
+4
-1
A tuning fork of frequency 480 Hz is used in an experiment for measuring speed of sound (v) in air by resonance tube method. Resonance is observed to occur at two successive lengths of the air column, l1 = 30 cm and l2 = 70 cm. Then, v is equal to -
A
338 ms–1
B
384 ms–1
C
379 ms–1
D
332 ms–1
3
JEE Main 2019 (Online) 12th April Evening Slot
+4
-1
A small speaker delivers 2 W of audio output. At what distance from the speaker will one detect 120 dB intensity sound ? [Given reference intensity of sound as 10–12 W/m2 ]
A
20 cm
B
10 cm
C
40 cm
D
30 cm
4
JEE Main 2019 (Online) 12th April Morning Slot
+4
-1
A progressive wave travelling along the positive x-direction is represented by y(x,t) = Asin(kx – $$\omega$$t + $$\phi$$). Its snapshot at t = 0 is given in the figure. For this wave, the phase $$\phi$$ is :
A
$${\pi \over 2}$$
B
$$\pi$$
C
0
D
$$- {\pi \over 2}$$
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