CBSE Class 12 Physics Communication Systems Assignment Set B

Communication Systems MCQ Questions with Answers Class 12 Physics 

Question- Encoding of signal is required for

(a) modulation at transmitting end

(b) modulation at receiving end

(c) demodulation at receiving end

(d) demodulation at transmitting end

Answer-(a)

Question- Range of communication is extended by using

(a) transmitter

(b) transducer

(c) processor

(d) repeater

Answer-(d)

Question- For transmission of e.m.wave of audible frequency, these waves are superimposed with waves of

(a) frequency less than 20 Hz

(b) frequency less than 10 KHz.

(c) frequency in the audible range.

(d) radio-frequency.

Answer-(d)

Question-In which of the following remote sensing technique is not used?

(a) Forest density

(b) Pollution

(c) Wetland mapping

(d) Medical treatment

Answer-(d)

Question- A radio station has two channels. One is AM at 1020 kHz and the other FM at 89.5 MHz. For good results you will use

(a) longer antenna for the AM channel and shorter for the FM

(b) shorter antenna for the AM channel and longer for the FM

(c) same length antenna will work for both

(d) information given is not enough to say which one to use for which

Answer-(a)

Question- For transmission of TV- signal, sound-part is

(a) amplitude modulated

(b) frequency modulated

(c) phase modulated

(d) pulse modulated

Answer-(b)

Question- Wave obtained on superimposition of audible frequency e.m. wave is known as

(a) carrier wave

(b) high frequency wave

(c) modulating wave

(d) modulated wave

Answer-(d)

Question- In sky-wave propagation, skip-distance depends on

(a) frequency of e.m. waves transmitted

(b) critical frequency of the layer

(c) height of layer above earth’s surface

(d) all of the above

Answer-(d)

Question-Which mode of communication is most suitable for carrier wave of frequencies around 100 MHz?

(a) Satellite

(b) Ground wave

(c) Line of sight

(d) Ionospheric

Answer-(c)

Question- The layer of atmosphere which contains water vapour is

(a) stratosphere

(b) mesospshere

(c) troposphere

(d) ionosphere

Answer-(c)

Question- Space wave communication is limited

(a) to the line of sight distance

(b) by earth’s curvature

(c) either (a) or (b)

(d) both (a) and (b)

Answer-(d)

Question-The waves used in telecommunication are

(a) IR

(b) UV

(c) Microwave

(d) Cosmic rays

Answer-(c)

36. Critical frequency that gets reflected back from ionosphere is

(a) same for all layers of the ionosphere

(b) different for different layers of the ionosphere

(c) not dependent on layers of the ionosphere

(d) None of these

Answer-(d)

Question-The losses in transmission lines are

(a) radiation losses only

(b) conductor heating only

(c) dielectric heating only

(d) all of these

Answer-(d)

Question- Which of the following is drawback of amplitude modulation?

(a) low efficiency

(b) noise reception

(c) operating range is small

(d) all of these

Answer-(d)

Question-Basic components of transmitter are

(a) message signal generator and antenna

(b) modulator and antenna

(c) signal generator and modulator and antenna

(d) message signal generator, modulator and antenna

Answer-(d)

Question-Which of the following device is fully duplex?

(a) Mobile phone

(b) Walky-talky

(c) Loud speaker

(d) Radio

Answer-(a)

Question- In Laser communication there is

(a) low loss of signal

(b) loss of signal

(c) no signal security

(d) low band width

Answer-(a)

Question-Citizen’s band ratio is the application of

(a) amplitude modulation

(b) frequency modulation

(c) phase modulation

(d) None of these

Answer-(a)

Question-A geosynchronous satellite is

(a) located at a height of 34860 km to ensure global coverage

(b) appears stationary over a place on earth’s magnetic pole

(c) not really stationary at all, but orbits the earth within 24 hours.

(d) always at fixed location in space and simply spins about its own axis

Answer-(c)

Question-During ground wave propagation the transmitted waves gets attenuated because

(a) earth surface absorbs the waves

(b) frequency of the waves are too low

(c) energy content of these waves are high

(d) earth surface offers resistance.

Answer-(d)