Physics Class 12

Physics class 12 chapter 15 Objective Questions

Communication Systems

  1. Which frequency range is used for TV transmission ? 

(A) 30 HZ – 300 Hz

(B) 30 KHZ – 300 kHZ

(C) 30 MHz – 300 MHz

(D) 30 GHz – 300 GHZ 

Answer : (C) 30 MHz – 300 MHz

  1. Sky wave communication is based upon : 

(A) reflection by ionosphere

(B) absorption by ionosphere

(C) transmission through ionosphere

(D) none of these 

Answer : (A) reflection by ionosphere

  1. The loss of strength of a signal while propagating though a medium is known as : 

(A) reception

(B) absorption

(C) transmission 

(D) attenuation

Answer : (D) attenuation

  1. The process of increasing the strength of a signal using an electronic circuit is called :

(A) amplification 

(B) modulation

(C) demodulation 

(D) transmission

Answer : (A) amplification 

  1. Modem is a device which performs : 

(A) modulation

(B) demodulation

(C) rectification

(D) modulation and demodulation 

Answer : (D) modulation and demodulation 

  1. The mode of propagation used by short wave broadcast services is : 

(A) space wave 

(B) sky wave

(C) ground wave 

(D) both ‘A’ and ‘C’

Answer : (B) sky wave

  1. Large bandwidth for higher data rate is achieved by using : 

(A) high frequency carrier wave

(B) high frequency audio wave

(C) low frequency carrier wave

(D) low frequency audio wave 

Answer : (A) high frequency carrier wave

  1. Who invented world wide web? 

(A) J.C.R. Licklider

(B) Tim Berners-Lee 

(C) Alexander Graham Bell

(D) Samuel F.B. Morse

Answer : (B) Tim Berners-Lee 

  1. The device which is a combination of a receiver and a transmitter is : 

(A) Amplifier 

(B) Repeater

(C) Transducer 

(D) Modulator

Answer : (B) Repeater

  1. Which of the following is not a transducer ? 

(A) Loudspeaker 

(B) Amplifier

(C) Microphone 

(D) All of these

Answer : (B) Amplifier

  1. Which of the following is an example of broadcast mode of communication?

(A) Radio 

(B) Television

(C) Mobile 

(D) Both A and B

Answer : (D) Both A and B

  1. The waves that are bent down by the ionosphere are:  

(A) ground waves 

(B) surface waves

(C) space waves 

(D) sky waves

Answer : (D) sky waves

  1. Who undertook the first space walk and in which year? 

(A) Leonov, 1965 

(B) Neil Armstrong, 1969

(C) Rakesh Sharma, 1998

(D) None of these

Answer : (A) Leonov, 1965 

  1. The term used to collect the information about an object and a place without physical contact” is called :

(A) modulation 

(B) communication

(C) amplification 

(D) remote sensing

Answer : (D) remote sensing

  1. The velocity of electromagnetic wave is : 

(A) 3 x 109 ms-1 

(B) 3 x 106 ms-1

(C) 3 x 108 ms-1 

(D) 3 x 1010 ms-1

Answer : (C) 3 x 108 ms-1 

  1. From which layer of atmosphere are radio waves reflected ? 

(A) Ionosphere 

(B) Mesosphere

(C) Chromosphere 

(D) None of the above 

Answer : (A) Ionosphere 

  1. The modulation index in amplitude modulation : 

(A) is always zero 

(B) lies between 0 and 1

(C) lies between 1 and

(D) can never exceed 0.5 

Answer : (B) lies between 0 and 1

  1. The output of a digital computer is an example of : 

(A) digital signal 

(B) analog signal

(C) both (A) and (B)

(D) neither (A) nor (B) 

Answer : (A) digital signal 

  1. Basically, a communication system is a : 

(A) transmitter 

(B) receiver

(C) messenger 

(D) All of these

Answer : (D) All of these

  1. Present day communication systems are : 

(A) electrical only

(B) electronic only

(C) optical only 

(D) All of the above 

Answer : (D) All of the above 

  1. Major parts of a communication system are : 

(A) transmitter and receiver 

(B) receiver and communication channel 

(C) transmitter and communication channel

(D) transmitter, receiver and communication channel 

Answer : (D) transmitter, receiver and communication channel 

  1. Frequencies in the UHF range normally propagate by means of :

(A) Ground wave 

(B) Sky waves

(C) Surface wave 

(D) Space wave

Answer : (D) Space wave

  1. The height of a TV transmission tower at any place on the surface of the earth is 245m. The maximum distance up to which transmission of tower will reach is :

(A) 245 m 

(B) 245 km 

(C) 56 km 

(D) 112 km

Answer : (C) 56 km 

  1. Modulation is of: 

(A) 2 types 

(B) 3 types

(C) 4 types 

(D) 5 types 

Answer : (B) 3 types

  1. Meaning of ‘FAX’ is : 

(A) Full Access Transmission

(B) Fascimile Telegraphy

(C) Factual Auto Access

(D) Feed Auto Exchange 

Answer : (B) Fascimile Telegraphy

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