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Statement-1: Sky wave signals are used f...

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

A

S-1 is false, S-2 is true

B

S-1 is true, S-1 is false

C

S-1 is true, S-2 is true, S-2 is the correct explanation of S-1

D

S-1 is true, S-2 is true, S-2 is not the correct explanation of S-1

Text Solution

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The correct Answer is:
B
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The 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 generel , less stable then ground wave signals statement - 2 : The state of inosphere varies from to hour day and season to season .

Statement-1: Short wave band are used for transmission fo radiowaves to a large distance. Statement-2: Short waves are reflected from ionosphere.

Statement-I : Television signals are received through sky-wave propagation Statement-II : The ionosphere reflects electromagnetic waves of frequencies greater than a certain critical frequency.

Statement-1 : Electromagnetic waves with frequencies smaller than the critical frequency of ionosphere cannot be used for communications using sky wave propagation. Statement-2: The refractive index of the ionosphere becomes very high for frequencies higher than the critical frequency.

Perhaps, the most commonly used mode of communication involves use of free space as a communication channel between transmitter and receiver. The various possible modes of using of free space have been described below Ground wave communication : This mode is used for low frequency as at high frequency, losses become large. This is useful for distance of the order of 1 km. Space wave communication: The signals are transmitted directly from transmitter to receiver. There is no limit to upper frequency, but its range is limited to few hundred kilometers. The range depends on the height of transmitting antenna Sky wave communication : The signals are sent towards sky They are reflected back towards earth by ionosphere. Its range can be above 500 km. But, very high frequencies (above 10 MHz) are not reflected back. Satellite communication: The signals that cannot be reflected back by ionosphere are reflected back by satellite. Moon is a passive satellite of earth. The frequency range allotted to FM radio broadcast is 88 MHz to 108 MHz. Which of the following communication channels can be used for its transmission? A. Sky wave communication only B. Space wave communication only C. Satellite communication only D. Either space wave communication or satellite communication

Statement-I : Electromagnetic waves with frequencies smaller than the critical frequency of ionosphere cannot be used for communication using sky wave propagation Statement-II : The refractive index of the ionosphere becomes very high for frequency.

Statement-1: We can use two photons successively of 1240 Å and 2000 Å wavelength in order to ionise a H-atom from ground state Statement-2: Sum of the energies of both the photons is greater than IE of H atom

What is line of sight communication? Why is it not possible to use sky waves for transmission of T.V. signals? Upto what distance can a signal be transmitted using an antenna of height h ?

Both amplitude modulation (AM) and frequency modulation (FM) are used for radio broadcasting. The amplitude of the high frequency carrier wave is varied or modulated in accordance with the variations in the amplitude of the audio signals that are to be transmitted, in te process of amplitude modulation in frequency modulation te amplitude of the carrier remains constant but its frequency is varied inn accordance withh the audio signal. Reception with AM signals is in general is affected by interference of various kinds ad elaborated equipment is required for FM broadcast. In india the radio signals are boarcast using-

Both amplitude modulation (AM) and frequency modulation (FM) are used for radio broadcasting. The amplitude of the high frequency carrier wave is varied or modulated in accordance with the variations in the amplitude of the audio signals that are to be transmitted, in te process of amplitude modulation in frequency modulation te amplitude of the carrier remains constant but its frequency is varied inn accordance withh the audio signal. Reception with AM signals is in general is affected by interference of various kinds ad elaborated equipment is required for FM broadcast. The rangeof a transmitter is

AAKASH SERIES-COMMUNICATION SYSTEM -LECTURE SHEET (LEVEL - I) (MAIN) (EXERCISE - IV) (Straight Objective & More than one Correct Answer Type Questions)
  1. Statement-1: Sky wave signals are used for long distance radio communi...

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  2. The highest frequency of radiowaves which when sent at some angle towa...

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  3. Speed of electromagnetic waves is the same

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  4. In space communication, the information can be passed from one place t...

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  5. Which one of the following is correct ?

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  6. The space wave propagation is utilized in

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  7. Three waves A,B and C of frequencies 1600 KHz, 5MHz and 60 MHz, respec...

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  8. A transmitter transmits the message in original

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  9. A receiver reconstructs the original message after propagation through...

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  10. A 100m long antenna is mounted on a 500m tall building. The complex ca...

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  11. A diode detector is used to detect an amplitude modulated wave of 60% ...

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  12. The number of telephone conversations by a fibre of band width 40MHz, ...

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  13. Which of the following devices is full duplex?

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  14. Which of the following devices is half duplex ?

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  15. Which of the following statement is wrong?

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  16. Through which mode of propagation the radio waves can be sent from one...

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  17. The maximum peak to peak voltage of an AM wire is 24 mV and the minimu...

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  18. In a communication system, noise is most likely to affect the signal

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  19. The radio waves of frequency 300 MHz to 3000 MHz belong to

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  20. Match the column I with column II.

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  21. Match the following elements of column I with their property given in ...

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