1
JEE Main 2020 (Online) 6th September Morning Slot
+4
-1
A sound source S is moving along a straight track with speed v, and is emitting, sound of frequency v0 (see figure). An observer is standing at a finite distance, at the point O, from the track. The time variation of frequency heard by the observer is best represented by:
(t0 represents the instant when the distance between the source and observer is minimum)
A
B
C
D
2
JEE Main 2020 (Online) 5th September Evening Slot
+4
-1
A driver in a car, approaching a vertical wall notices that the frequency of his car horn, has changed from 440 Hz to 480 Hz, when it gets reflected from the wall. If the speed of sound in air is 345 m/s, then the speed of the car is :
A
36 km/hr
B
54 km/hr
C
24 km/hr
D
18 km/hr
3
JEE Main 2020 (Online) 5th September Evening Slot
+4
-1
Two coherent sources of sound, S1 and S2, produce sound waves of the same wavelength, $$\lambda$$ = 1 m, in phase. S1 and S2 are placed 1.5 m apart (see fig). A listener, located at L, directly in front of S2 finds that the intensity is at a minimum
when he is 2 m away from S2. The listener moves away from S1, keeping his distance from S2 fixed. The adjacent maximum of intensity is observed when the listener is at a distance d from S1. Then, d is :
A
12 m
B
2 m
C
3 m
D
5 m
4
JEE Main 2020 (Online) 4th September Evening Slot
+4
-1
The driver of a bus approaching a big wall notices that the frequency of his bus's horn changes from 420 Hz to 490 Hz when he hears it after it gets reflected from the wall. Find the speed of the bus if speed of the sound is 330 ms–1.
A
91 kmh–1
B
81 kmh–1
C
61 kmh–1
D
71 kmh–1
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