CBSE
Multiple Choice QuestionsFor satellite communication which wave is used
Space wave
Sky wave
Ground wave
Microwave
A sound absorber attenuates the sound level by 20 dB. The intensity decreases by a factor of
1000
10000
10
100
A hemisphere is positively charged uniformly. The electric field at a point on a diameter away from the centre is directed
perpendicular to the diameter
parallel to the diameter
at an angle tilted towards the diameter
at an angle tilted away from the diameter
If modulation index is 1/2 and power of carrier wave is 2 W. Then what will be the total power in modulated wave?
0.5 W
1 W
0.25 W
2.25 W
Two sources of sound placed close to each other, are emitting progressive waves given by
y1 = 4sin 600π t and y2 = 5 sin 608πt
An observer located near these two sources of sound will hear
4 beats per second with intensity ratio 25: 16 between waxing and waning
8 beats per second with intensity ratio 25:16 between waxing and waning
8 beats per second with intensity ratio 81:1 between waxing and waning
8 beats per second with intensity ratio 81:1 between waxing and waning
A source emits electromagnetic waves of wavelength 3m. One beam reaches the observer directly and other after reflection from a water surface, travelling 1.5 m extra distance and with an intensity reduced to 1/4 as compared to intensity due to the direct beam alone. The resultant intensity will be.
(1/4) fold
(3/4) fold
(5/4) fold
(9/4) fold
Assertion: Short wave communication over long distance is not possible via ground waves.
Reason: The ground waves can bend round the corners ofthe objects on earth.
If both assertion and reason are true and reason is the correct explanation of assertion.
If both assertion and reason are true but reason is not the correct explanation of assertion.
If assertion is true but reason is false.
If both assertion and reason are false.
Long distance communication between two point or earth is achieved by
Space wave communication
Sky wave communication
Satellite wave communication
Line of sight transmission
What maximum frequency can be reflected from ionosphere?
5 MHz
6 GHz
5 KHz
500 MHz
Assertion: Sky wave signals are used for long distance radio communication. These signals are in general, less stable than ground wave signals.
Reason: The state of ionosphere varies from hour to hour, day to day and season to season.
If both assertion and reason are true and reason is the correct explanation of assertion.
If both assertion and reason are true but reason is not the correct explanation of assertion.
If assertion is true but reason is false.
If both assertion and reason are false.
