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 Multiple Choice QuestionsMultiple Choice Questions

1.

Arrange the following electromagnetic radiations per quantum in the order of increasing energy:

A: Blue light
B: Yellow light
C: X-ray
D: Radiowave

  • D, B, A, C

  • A, B, D, C

  • C, A, B, D

  • C, A, B, D

294 Views

2.

Choose the correct statement:

  • In amplitude modulation, the amplitude of the high-frequency carrier wave is made to vary in proportion to the amplitude of the audio signal.

  • In amplitude modulation, the frequency of the high-frequency carrier wave is made to vary in proportion to the amplitude of the audio signal.

  • In frequency modulation, the amplitude of the high-frequency carrier wave is made to vary in proportion to the amplitude of the audio signal.

  • In frequency modulation, the amplitude of the high-frequency carrier wave is made to vary in proportion to the amplitude of the audio signal.

214 Views

3.

A signal of 5 kHz frequency is amplitude modulated on a carrier wave of frequency 2 MHz. The frequencies of the resultant signal is/are:

  • 2005 kHz, and 1995 kHz

  • 2005 kHz, 2000 kHz and 1995 kHz

  • 2000 kHz and 1995 kHz

  • 2000 kHz and 1995 kHz

397 Views

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4.

A train is moving on a straight track with speed 20 ms-1 .It is blowing its whistle at the frequency of 1000 Hz. The percentage change in the frequency heard by a person standing near the track as the train passes him is (speed of sound = 320 ms-1 ) close to :

  • 6%

  • 12%

  • 18%

  • 18%


B.

12%

Apparent frequency heard by the person before crossing the train.

straight f subscript 1 space equals space open parentheses fraction numerator straight c over denominator straight c minus straight v subscript straight s end fraction close parentheses space straight f subscript straight o space equals space open parentheses fraction numerator 320 over denominator 320 minus 20 end fraction close parentheses space 1000
Similarly, apparent frequency heard, after crossing the trainsstraight f subscript 2 space equals space open parentheses fraction numerator straight c over denominator space straight c plus straight V subscript straight s end fraction close parentheses straight f subscript straight o space equals space open parentheses fraction numerator 320 over denominator 320 plus 20 end fraction close parentheses 1000
left square bracket straight c space equals speed space of space sound right square bracket
increment straight f space equals space straight f subscript 1 minus straight f subscript 2 space equals space open parentheses fraction numerator 2 cv over denominator straight c squared minus straight v subscript straight s superscript 2 end fraction close parentheses straight x space straight f subscript straight o
or space fraction numerator increment straight f over denominator straight f subscript straight o end fraction straight x 100 space equals space open parentheses fraction numerator 2 cv over denominator straight c squared minus straight v subscript straight s superscript 2 end fraction close parentheses straight x 100
space equals space fraction numerator 2 space straight x space 320 space straight x space 20 over denominator 300 space straight x space 340 end fraction straight x 100
equals space fraction numerator 2 space space straight x space 32 space straight x space 20 over denominator 3 space straight x 34 end fraction space equals space 12.54 space equals space 12 percent sign

472 Views

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5.

A diode detector is used to detect an amplitude modulated wave of 60% modulation by using a condenser of capacity 250 pico farad in parallel with a load resistance 100 kilo ohm. Find the maximum modulated frequency which could be detected by it. 

  • 10.62 MHz

  • 10.62 kHz

  • 5.31 mHz

  • 5.31 mHz

313 Views

6.

A radar has a power of 1 Kw and is operating at a frequency of 10 GHz. It is located on a mountain top of height 500 m. The maximum distance upto which it can detect object located on the surface of the earth (Radius of earth = 6.4 x 106 m) is

  • 80 km

  • 16 km

  • 40km

  • 40km

321 Views

7.

This question has Statement 1 and Statement 2. Of the four choices given after the statements, choose the one that best describes the two statements. 
Statement 1 - Sky wave signals are used for long distance radio communication. These signals are in general, less stable than ground wave signals.
Statement 2- The state of ionosphere varies from hour to hour, day to day and season to season.

  •  Statement 1 is true, statement 2 is false. 

  • Statement 1 is true, Statement 2 is true, Statement 2 is the correct explanation of Statement 1

  •  Statement 1 is true, Statement 2 is true, Statement 2 is not the correct explanation of Statement 1

  •  Statement 1 is true, Statement 2 is true, Statement 2 is not the correct explanation of Statement 1

233 Views

8.

A sound absorber attenuates the sound level by 20 dB. The intensity decreases by a factor of

  • 1000

  • 10000

  • 10

  • 10

491 Views

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9.

In a full wave rectifier circuit operating from 50 Hz mains frequency, the fundamental frequency in the ripple would be

  • 50 Hz

  • 25 Hz

  • 100 Hz

  • 100 Hz

285 Views

10.

A telephonic communication service is working at carrier frequency of 10 GHz. Only 10% of it is utilized for transmission. How many telephonic channels can be transmitted simultaneously if each channel requires a bandwidth of 5 kHz?

  • 2 x 106

  • 2 x 105

  • 2 x 104

  • 2 x 105


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