Waves Test

Result

Waves Test - 97

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Weekly Quiz Competition

Question 1
4 / -1

The difference between the apparent frequency of a source of sound as perceived by an observer during its approach and recession is 2% of the natural frequency of the source. If the velocity of sound in air is 300 m/sec, the velocity of the source is (It is given that velocity of source < < velocity of sound)

A
6 m/sec

B
3 m/sec

C
1.5 m/sec

D
12 m/sec

Solution
Question 2
4 / -1

A plane EM wave of frequency 30 MHz travels in free space along the x-direction. The electric field component of the wave at a particular point of space and time E = 6V/m along y-direction. Its magnetic field component B at this point would be

A
2 x 10^–8 T along z-direction

B
6 x 10^–6T along x-direction

C
2 x 10^–8T along y-direction

D
6 x 10^–8T along z-direction

Solution
Question 3
4 / -1

Two cars are moving on two perpendicular roads towards a crossing with uniform speeds of 72 km/hr and 36 km/hr. If first car blows horn of frequency 280 Hz, then the frequency of horn heard by the driver of second car when line joining the cars make 45° angle with the roads; will be

A
321 Hz

B
298 Hz

C
289 Hz

D
280 Hz

Solution
Question 4
4 / -1

Two whistles A and B produce notes of frequencies 660 Hz and 596 Hz respectively. There is a listener at the mid-point of the line joining them. Now the whistle B and the listener start moving with speed 30 m/s away from the whistle A. If speed of sound be 330 m/s, how many beats will be heard by the listener?

A
2

B
4

C
6

D
8

Solution
Question 5
4 / -1

An observer moves towards a stationary source of sound with a speed 1/5th of the speed of sound. The wavelength and frequency of the source emitted are X and f respectively. The apparent frequency and wavelength recorded by the observer are respectively

A
1.2f, λ

B
f, 1.2 λ

C
0.8 f, 0.8 λ

D
1.2 f, 1.2 λ

Solution
Question 6
4 / -1

A light pointer fixed to one prong of a tuning fork touches a vertical plate. The fork is set vibrating and the plate is allowed to fall freely. If eight oscillations are counted when the plate falls through 10 cm, the frequency of the tuning fork is

A
360 Hz

B
280 Hz

C
560 Hz

D
56 Hz

Solution
Question 7
4 / -1

Oxygen is 16 times heavier than hydrogen. Equal volumes of hydrogen and oxygen are mixed. The ratio of speed of sound in the mixture to that in hydrogen is

A

B

C

D

Solution
Question 8
4 / -1

A
1 : 2

B
2 : 1

C
1 : 1

D
None of these

Solution
Question 9
4 / -1

A

B

C

D

Solution
Question 10
4 / -1

Consider ten identical sources of sound all giving the same frequency but having phase angles which are random. If the average intensity of each source is I_o, the average of resultant intensity I due to all these ten sources will be

A

B

C

D

Solution