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Correct option is (a) ITU

To elaborate: The International Telecommunications Union (ITU), an agency of the UNITED NATIONS that is headquartered in GENEVA, Switzerland, comprises 189 member countries that meet at regular intervals to promote cooperation and negotiate national interests. The ITU brings together the various countries

to discuss how the frequency spectrum is to be divided up and shared. Because many of the signals generated in the spectrum do not carry for long distances, countries can use these frequencies simultaneously without interference.

Right answer is (a) True

The BEST explanation: The BENEFIT of using the higher frequencies for communication carriers is that a signal of a given bandwidth represents a smaller percentage of the SPECTRUM at the higher frequencies than at the LOWER frequencies. It means that there can be more number of channels with the same bandwidth in higher frequency than lower frequencies.

Right option is (b) Bandwidth

Explanation: Bandwidth is that portion of the electromagnetic spectrum OCCUPIED by a signal. It is also the frequency RANGE over which a receiver or other electronic circuit OPERATES. More specifically, bandwidth is the difference between the upper and lower frequency LIMITS of the signal or the EQUIPMENT operation range.

The correct ANSWER is (c) Stopped by ionizing effects

Explanation: X-rays are not stopped by ionizing effects and that was the only reason they were ever thought they could be USED in communication. In re-entry vehicles, a temporary communication cut off is EXPERIENCED due to ionizing effects. X- rays were hard to modulate and focus and hence GRADUALLY let down.

Correct option is (d) Books

Best explanation: Infrared radiation is GENERALLY associated with heat. Infrared is PRODUCED by light bulbs, HUMAN bodies, and basically any physical EQUIPMENT that generates heat.

Right choice is (c) 1477.8Mhz

For EXPLANATION I would SAY: WAVELENGTH =8 in.= 0.203 m

Frequency = 300/0.203 = 1477.8Mhz.

The correct ANSWER is (b) Satellite communication

The explanation: SHFS or Super High Frequency EM waves are those which LIE between the frequency range of 3 to 30GHz range. These microwaves frequencies are widely used in satellite communication and RADAR.

The CORRECT option is (b) Wavelength

Explanation: The wavelength of a WAVE is the distance the wave TRAVELS in one cycle. The wavelength of a signal is represented by the Greek letter λ (lambda) and has the same UNITS as length.

The correct choice is (c) EM spectrum

To EXPLAIN: The range of ELECTROMAGNETIC signals encompassing all FREQUENCIES is referred to as Electromagnetic spectrum. It includes RADIO waves, microwaves, optical waves, x-rays, gamma rays and cosmic waves.

Right answer is (a) Less noise

The best I can EXPLAIN: ALTHOUGH AM is much simpler and has a WIDER RANGE due to atmospheric propagation, one of its MAJOR disadvantages is due to noise. Noise directly affects the amplitude of the signal and its hard to retrieve the original information.

Correct choice is (a) FREQUENCY

To explain I would say: CPS or cycles PER SECOND is an alternative unit for the frequency of an EM wave. The other unit for frequency is Hertz which is more commonly used AROUND the world.

The correct option is (a) TIME division multiplexing

For explanation: In serial buses, time division multiplexing is used to split the digital data, which is in binary NUMBERS, into individual bits which occupy a particular time slot and is TRANSMITTED. The use of serial buses increases the limit on transmission SPEED and reduces NOISE.

The CORRECT ANSWER is (c) Pulse modulation

Explanation: Modulation is of three types, frequency modulation, AMPLITUDE modulation and PHASE modulation. Pulse modulation is a TYPE of amplitude modulation.

Correct OPTION is (c) Amplitude of the carrier wave

Easiest explanation: In amplitude modulation, the amplitude of the carrier wave is modulated with respect to the INFORMATION signal. The frequency and the PHASE of both the carrier and the information signal REMAIN constant.

Right ANSWER is (a) True

The best explanation: In frequency modulation, the baseband signal is overlapped or impressed in the carrier signal. The carrier can never have a lower frequency than the baseband signal as it WOULD result in a huge DATA loss of the baseband signal.

Right CHOICE is (a) True

Explanation: Baseband signals are, in many cases, incompatible with the MEDIUM. Theoretically, it is possible to transmit voice signals DIRECTLY by radio, but due to the low frequency of these waves the antenna size REQUIRED form transmission is too big.

Correct option is (c) Baseband signal

For EXPLANATION I would say: The information signal, regardless of analog or digital type, is REFERRED to as baseband signals. It could be voice, VIDEO or digital data and is modulated before TRANSMISSION. In some case, baseband signals can be TRANSMITTED without modulation.

The correct choice is (b) Digital

Explanation: In digital COMMUNICATION, the information can be quantized and TRANSMITTED. In TIME division multiplexing the information or digital data is quantized and transmitted in time slots which can be PUT together to get the ORIGINAL information.

Right choice is (C) Half duplex

For explanation: Ia a walkie talkie the COMMUNICATION is two WAY but at a GIVEN time only one way communication is allowed. This type of communication is called as half duplex communication.

The correct ANSWER is (d) WALKIE TALKIE

The explanation: A SIMPLEX communication is when signal is sent from one end and is received at the other end. The communication in a walkie talkie is a two way communication.

Correct option is (d) Permeability and permittivity of medium

Explanation: SINCE the EM WAVES are made of electric and magnetic fields, the resistance GIVEN by the medium to conduct electric and magnetic waves DETERMINE the SPEED of the EM wave. This is given by the permeability and the permittivity of the medium.

Correct option is (b) False

The explanation: Radio waves TRAVEL at the speed of LIGHT only in FREE space. Other all communication medium attenuates the signal and lowers the speed of signal PROPAGATION.

The correct answer is (b) Duplexer

The explanation is: A transceiver is a device that contains the necessary ELECTRONIC COMPONENTS for both transmission and RECEIVING in the same medium. They have a common power supply and a common antenna for transmitting and receiving.

Correct option is (a) True

For EXPLANATION I would say: EARTH can be considered as a COMMUNICATION medium as it can carry low frequency sound WAVES as well as conduct electricity. Communication for some submarines uses earth as a communication medium.

Right choice is (c) SONAR

Easiest explanation: SONAR or SOund Navigation and RANGING is the transmission of INFORMATION using sound waves. Since seawater is saline, it shorts out the electrical field in the radio waves and hence radio communication cannot be USED.

The correct choice is (a) Transmitter

Explanation: A transmitter is an electronic COMPONENT that CONVERTS the electric signals into a signal that is suitable for TRANSMISSION in any given MEDIUM. It could be WIRES, air, water, land or even space.

Right ANSWER is (a) Heinrich Hertz

Best explanation: The GERMAN physicist, Heinrich Hertz, first applied the theory GIVEN by Maxwell to prove the existence of RADIO waves in 1887. To honor him the unit of FREQUENCY is given his name.