JEE Physics

StemEZ

Chapter 20

Communication Systems - all with Video Answers

Educators

+ 2 more educators

Chapter Questions

Problem 2668

Type of communication Possible by Modem duplex is
(A) Half duplex
(B) Simplex
(C) Double Duplex
(D) Full duplex

Kamlesh Goyal

Kamlesh Goyal

Numerade Educator

Problem 2669

To transmit $1 \mathrm{KHz}$ frequency signal, wave length of the signal should be $\quad \mathrm{m}$.
(A) $3 \times 10^{3}$
(B) $3 \times 10^{5}$
(C) $3 \times 10^{7}$
(D) $3 \times 10^{10}$

Gopal Sharma

Numerade Educator

Problem 2670

What should be the minimum length of the antenna capable of emitting audio signal of wave length $\lambda ?$
(A) $(\lambda 4)$
(B) $(N 8)$
(C) $\lambda$
(D) $(\lambda 2)$

Gopal Sharma

Numerade Educator

Problem 2671

is used as a medium in space communication
(A) Two wire line
(B) Space
(C) Amplifier
(D) Optical fibre

Gopal Sharma

Numerade Educator

Problem 2672

The band width of Audio signal is
(A) $20 \mathrm{HZ}$
(B) $20 \mathrm{KHZ}$
(C) $20 \mathrm{MHZ}$
(D) $20 \mathrm{GHZ}$

Gopal Sharma

Numerade Educator

Problem 2673

ground waves are polarised at direction.
(A) vertically upward
(B) horizontal
(C) tangential direction to the surface of the earth
(D) in all four.

Gopal Sharma

Numerade Educator

Problem 2674

Intensity of electric field of ground waves is in of the distance travelled by it.
(A) Square
(B) inverse of root
(C) proportion
(D) inverse

Gopal Sharma

Numerade Educator

Problem 2675

In radio and television broadcast, the information signal is in the form of
(A) analog signal
(B) digital signal
(C) Both analog and digit signals
(D) neither analog nor digital signal

Gopal Sharma

Numerade Educator

Problem 2676

In light modulation, which characteristics of the carrier light Wave is varied?
(A) Amplitude
(B) Frequency
(C) Phase
(D) intensity

Gopal Sharma

Numerade Educator

Problem 2677

Though which mode of communication can radio waves be sent from one Plate to another?
(A) Ground wave Propagation
(B) sky wave Propagation
(C) Space wave Propagation
(D) All of the above

Gopal Sharma

Numerade Educator

Problem 2678

Which range of Frequencies is Suitable for sky wave Propagation ?
(A) $1 \mathrm{KHZ}$ to $500 \mathrm{KHZ}$
(B) $1 \mathrm{MHZ}$ to $2 \mathrm{MHZ}$
(C) $2 \mathrm{MHZ}$ to $20 \mathrm{MHZ}$
(D) Above $30 \mathrm{MHZ}$

Gopal Sharma

Numerade Educator

Problem 2679

Which of the Following is not a component of communication System?
(A) Transmitter
(B) Transmission channel
(C) Noise
(D) Receiver

Gopal Sharma

Numerade Educator

Problem 2680

Device which transform one form of energy in to another form of energy is called a
(A) Transducer
(B) Transformer
(C) Transponder
(D) Transistor

Gopal Sharma

Numerade Educator

Problem 2681

is a link between the transmitter and receiver
(A) Microphone
(B) Transmission Channel
(C) transducer
(D) telephone

Gopal Sharma

Numerade Educator

Problem 2682

in the receiver section are used to reduce the level of noise signal
(A) filter circuit
(B) Modulator
(C) de modulator
(D) Amplifier

Gopal Sharma

Numerade Educator

Problem 2683

The maximum distance a up to which T.V transmission from a T.V. tower of height $h$ can be received is Proportional to
(A) $\mathrm{h}^{(1 / 2)}$
(B) $\mathrm{h}$
(C) $\mathrm{h}^{(3 / 2)}$
(D) $\mathrm{h}^{2}$

Gopal Sharma

Numerade Educator

Problem 2684

The energy attenuation in optical fiber is mainly due to
(A) absorption
(B) scattering
(C) both a and $\mathrm{b}$
(D) neither absorption nor scattering

Gopal Sharma

Numerade Educator

Problem 2685

The electromagnetic waves of frequency $2 \mathrm{MHz}$ to $30 \mathrm{MHz}$ are
(A) in ground wave propagation
(B) in sky wave propagation
(C) in micro wave propagation
(D) in satellite communication

Gopal Sharma

Numerade Educator

Problem 2686

Coaxial cable offers a band width approximately $\mathrm{MHz}$
(A) 1
(B) 20
(C) 250
(D) 1000

Gopal Sharma

Numerade Educator

Problem 2687

Modulation is used to
(A) reduce the band width used
(B) separate the transmission of different areas
(C) ensure that information may be transmitted to long distance
(D) allow the use of practical antennas

Gopal Sharma

Numerade Educator

Problem 2688

An antenna can transmit $\quad$ radiation with more efficiency.
(A) low frequency
(B) high frequency
(C) long wave length
(D) None of these

Prem Bijarniya

Numerade Educator

Problem 2689

For an amplitude modulated wave, the maximum amplitude is found to be $9 \mathrm{~V}$ while the minimum amplitude is found to be $3 \mathrm{~V}$. The modulation index is
(A) $100 \%$
(B) $75 \%$
(C) $50 \%$
(D) $25 \%$

Gopal Sharma

Numerade Educator

Problem 2690

AM is used for broadcasting because
(A) it is more noise immune than other modulation system
(B) it requires less transmitting power compared with other system
(C) it avoids receiver complexity
(D) No other modulation system can provide the necessary band width faithful transmission

Gopal Sharma

Numerade Educator

Problem 2691

Frequencies in the UHF range normally propagate by means of
(A) ground waves
(B) sky waves
(C) surface waves
(D) space waves

Nishant Kumar

Numerade Educator

Problem 2692

The area to be covered for T.V telecast is doubled. Then the height to transmitting antenna will have to be
(A) doubled
(B) halved
(C) quadrupled
(D) kept unchanged

Gopal Sharma

Numerade Educator

Problem 2693

Which of the following is related to telecommunication
(A) X-rays
(B) r-rays
(C) sound wave
(D) microwaves

Gopal Sharma

Numerade Educator

Problem 2694

Suppose the amplitude of modulated wave equal to the signal amplitude. Then modulation is
(A) $10 \%$
(B) $25 \%$
(C) $50 \%$
(D) $100 \%$

Gopal Sharma

Numerade Educator

Problem 2695

Space waves are generally propagated in
(A) UHF
(B) VHF
(C) HF
(D) None of there

Gopal Sharma

Numerade Educator

Problem 2696

If the frequency of $3 \mathrm{KHz}$ has to be transmitted through amplitude modulation. Which of the following frequency should use as a carrier frequency?
(A) $30 \mathrm{~Hz}$
(B) $300 \mathrm{~Hz}$
(C) $3000 \mathrm{~Hz}$
(D) $3 \mathrm{MHz}$

Gopal Sharma

Numerade Educator

Problem 2699

A T.V tower has a height $150 \mathrm{~m}$. What is the population density around the T.V tower if the total population covered is 50 lakh ? (Radius of earth $=6.4 \times 10^{6} \mathrm{~m}$ )
(A) $82.6 / \mathrm{km}^{2}$
(B) $800.6 / \mathrm{km}^{2}$
(C) $828.6 / \mathrm{km}^{2}$
(D) $876.6 / \mathrm{km}^{2}$

Gopal Sharma

Numerade Educator

Problem 2700

In which frequency range, space waves are normally propagated ?
(A) HF
(B) VHF
(C) UHF
(D) SHF

Gopal Sharma

Numerade Educator

Problem 2701

If $\mathrm{M}_{1} \& \mathrm{M}_{2}$ are the refractive indices of the material of core and cladding of an optical fiber, than the loss of light due to its leakage can be minimized by having
(A) $\mathrm{M}_{1}>\mathrm{M}_{2}$
(B) $\mathrm{M}_{1}<\mathrm{M}_{2}$
(C) $\mathrm{M}_{1}=\mathrm{M}_{2}$
(D) None of these

Gopal Sharma

Numerade Educator

Problem 2702

Through which mode of propagation, the radio waves can be sent from one place to another ?
(A) ground wave propagation
(B) sky wave propagation
(C) space wave propagation
(D) all of them

Arpit Gupta

Numerade Educator

Problem 2703

A radio can tune to any station in the 7. $5 \mathrm{MHz}$ to $12 \mathrm{MHz}$ band. What is the corresponding wave length band?
(A) $400 \mathrm{~m}-250 \mathrm{~m}$
(B) $40 \mathrm{~m}-25 \mathrm{~m}$
(C) $4 \mathrm{~m}-2.5 \mathrm{~m}$
(D) None of these

Gopal Sharma

Numerade Educator

Problem 2704

In the following question from statement-1 (Assertion) is followed by statement-2 (Reason) Each question has the following four choice out of which only one choice is correct
(a) Statement $-1$ is true, statement $-2$ is true. Statement- 2 is a correct explanation for statement-1.
(b) Statement-1 is true, statement-2 is true, statement $-2$ is not a correct explanation for statement $-1$.
(c) Statement $-1$ is true, statement- 2 is false
(d) Statement-1 is false, statement- 2 is true.
Statement-1 :- sky waves are not used in the transmission of
T.V signals Statement-2 :- T.V signals have a frequency range of 100 to $200 \mathrm{MHz}$
(A) a
(B) $\mathrm{b}$
(C) $\mathrm{c}$
(D) d

Gopal Sharma

Numerade Educator

Problem 2705

In the following question from statement-1 (Assertion) is followed by statement-2 (Reason) Each question has the following four choice out of which only one choice is correct
(a) Statement- 1 is true, statement $-2$ is true. Statement- 2 is a correct explanation for statement $-1 .$
(b) Statement-1 is true, statement-2 is true, statement-2 is not a correct explanation for statement-1.
(c) Statement- 1 is true, statement $-2$ is false
(d) Statement- 1 is false, statement $-2$ is true.
Statement-1 :- Micro waves and not radio waves are used in satellite communication. Statement-2 :-The wavelength of microwaves is much shorter than that of radio waves. Hence micro wave do not disperse or diffract like radio waves.
(A) a
(B) $\mathrm{b}$
(C) $\mathrm{c}$
(D) d

Gopal Sharma

Numerade Educator

Problem 2706

In the following question from statement-1 (Assertion) is followed by statement-2 (Reason) Each question has the following four choice out of which only one choice is correct
(a) Statement- 1 is true, statement $-2$ is true. Statement $-2$ is a correct explanation for statement-1.
(b) Statement-1 is true, statement-2 is true, statement-2 is not a correct explanation for statement-1.
(c) Statement- 1 is true, statement $-2$ is false
(d) Statement-1 is false, statement $-2$ is true.
Statement-1 :- sky wave communication is not suitable for frequencies greater than $30 \mathrm{MHz}$. Statement $-2:-$ High frequency signals die out before reaching the ionosphere.
(A) a
(B) $b$
(C) $c$
(D) $\mathrm{d}$

Gopal Sharma

Numerade Educator

Problem 2707

In the following question from statement-1 (Assertion) is followed by statement-2 (Reason) Each question has the following four choice out of which only one choice is correct
(a) Statement-1 is true, statement-2 is true. Statement-2 is a correct explanation for statement-1.
(b) Statement-1 is true, statement- 2 is true, statement-2 is not a correct explanation for statement-1.
(c) Statement-1 is true, statement-2 is false
(d) Statement-1 is false, statement- 2 is true.
Statement-1 :- Modulated wave is received directly on a head phone Statement- $2:-$ High frequency waves are beyond audible range.
(A) a
(B) $\mathrm{b}$
(C) $\mathrm{c}$
(D) d

Khoobchandra Agrawal

Khoobchandra Agrawal

Numerade Educator

Problem 2708

The refractive index of the ionosphere
(A) increase as we go from the lower to upper layer of the ionosphere
(B) decrease as we go from the lower to upper layer of the ionosphere
(C) remain the same through out the ionosphere
(D) is equal to unity

Mirza Aslam Beig

Mirza Aslam Beig

Numerade Educator

Problem 2709

A T.V tower has a height of $80 \mathrm{~m}$. The maximum distance up to which T.V transmission can be received is equal to (radius of earth $=6.4 \times 10^{6} \mathrm{~m}$ )
(A) $16 \mathrm{~km}$
(B) $32 \mathrm{~km}$
(C) $80 \mathrm{~km}$
(D) $160 \mathrm{~km}$

Gopal Sharma

Numerade Educator

Problem 2710

A receiving station on the ground is receiving a signal of frequency $10 \mathrm{MHz}$, then the mode of transmission is
(A) ground wave propagation
(B) sky wave propagation
(C) both ground wave and sky wave propagation
(D) neither ground wave nor sky wave propagation

Gopal Sharma

Numerade Educator

Problem 2711

On a particular day, the maximum frequency reflected from the ionosphere is $8 \mathrm{MHz}$. On another day it was found to increase to $9 \mathrm{MHz}$. The ratio of the maximum electron densities of ionosphere on the two days is
(A) $\sqrt{(8 / 9)}$
(B) $(8 / 9)$
(C) $(8 / 9)^{(3 / 2)}$
(D) $(8 / 9)^{2}$

Gopal Sharma

Numerade Educator

Problem 2712

Consider an optical communication system operating at $\lambda=800 \mathrm{~nm}$. Suppose only $1 \%$ of the optical source frequency is the available channel bandwidth for optical communication. No. of channels that can be accommodated for transmitting video $\mathrm{T}$. $\mathrm{V}$ signals requiring an approximate band width of $4.5 \mathrm{MHz}$ is
(A) $3.8 \times 10^{+14}$
(B) $3.8 \times 10^{12}$
(C) $8.4 \times 10^{5}$
(D) $1.71 \times 10^{7}$

Gopal Sharma

Numerade Educator

Problem 2713

A signal $\mathrm{e}_{\mathrm{m}}=20 \sin 2000 \pi \mathrm{t}$ amplitude modulates a carries wave $e_{c}=80 \sin 200000 \pi t$. The percentage of modulation is
(A) $25 \%$
(B) $0.25 \%$
(C) $400 \%$
(D) $40 \%$

Gopal Sharma

Numerade Educator

Problem 2714

A transmitting antenna at the top of a tower has a height of $50 \mathrm{~m}$ and the height of the receiving antenna is $32 \mathrm{~m}$. The maximum distance between them for satisfactory communication in line of sight mode is Given radius of earth $\mathrm{R}=6400 \mathrm{~km}$
(A) $25.29 \times 10^{3} \mathrm{~km}$
(B) $20.23 \times 10^{3} \mathrm{~km}$
(C) $45.5 \mathrm{~km}$
(D) None of these.

Gopal Sharma

Numerade Educator

Problem 2715

The characteristic impedance of a co-axial cable is between
(A) $10 \Omega$ to $20 \Omega$
(B) $20 \Omega$ to $30 \Omega$
(C) $30 \Omega$ to $60 \Omega$
(D) $50 \Omega$ to $70 \Omega$

Mirza Aslam Beig

Mirza Aslam Beig

Numerade Educator

Problem 2716

The relation between the maximum electron density $\mathrm{N}$ max and the critical frequency $\mathrm{f}$ for the ionosphere can be given as
(A) $\left.f_{c}=\sqrt{(9 N}_{\max }\right)$
(B) $\mathrm{f}_{\mathrm{c}}=\sqrt{9}\left(\mathrm{~N}_{\max }\right)$
(C) $\left.f_{c}=9 \sqrt{(N}_{\max }\right)$
(D) None of these

Mirza Aslam Beig

Mirza Aslam Beig

Numerade Educator

Problem 2717

In order to cover a circular region of radius $128 \mathrm{~km}$, by a TV transmitter, What must be the height of the transmitting antenna ?
(A) $79 \mathrm{~m}$
(B) $1050 \mathrm{~m}$
(C) $1280 \mathrm{~m}$
(D) $1560 \mathrm{~m}$

Mirza Aslam Beig

Mirza Aslam Beig

Numerade Educator

Problem 2718

The frequency of carries wave emitted from $L-C$ oscillator of $10 \mu \mathrm{H}$ inductance and $1 \mathrm{nF}$ capacitor is
(A) $1592 \mathrm{KHz}$
(B) $1592 \mathrm{~Hz}$
(C) $1592 \mathrm{MHz}$
(D) $159.2 \mathrm{~Hz}$

Mirza Aslam Beig

Mirza Aslam Beig

Numerade Educator

Problem 2719

If the band width is $1.6 \times 10^{12} \mathrm{~Hz}$, how many communication channels can be obtained with $16 \mathrm{KHz}$ band width radio signal ?
(A) $10^{15}$
(B) $10^{11}$
(C) $10^{10}$
(D) $10^{8}$

Nidhi Singhi

Numerade Educator

Problem 2720

A transmitter transmit a power of $10 \mathrm{KW}$ when modulation is $50 \%$. What is the power of carrier wave?
(A) $12 \mathrm{KW}$
(B) $7.0 \mathrm{KW}$
(C) $8.89 \mathrm{KW}$
(D) $5.0 \mathrm{KW}$

Mirza Aslam Beig

Mirza Aslam Beig

Numerade Educator

Problem 2721

A T.V. tower has a height $200 \mathrm{~m}$. By how much the height of tower be increased to triple its coverage range ?
(A) $1600 \mathrm{~m}$
(B) $800 \mathrm{~m}$
(C) $1800 \mathrm{~m}$
(D) $600 \mathrm{~m}$

Mirza Aslam Beig

Mirza Aslam Beig

Numerade Educator

Problem 2722

In short wave communication wave of which of the following frequencies will be reflected back by the ionosphere layer having electron density $1.23 \times 10^{12} \mathrm{~m}$
(A) $2 \mathrm{MHz}$
(B) $10 \mathrm{MHz}$
(C) $12 \mathrm{MHz}$
(D) $18 \mathrm{MHz}$

Mirza Aslam Beig

Mirza Aslam Beig

Numerade Educator

Problem 2723

What is the frequency range of signals that can be transmitted in care of twisted pair of wires ?
(A) $5 \mathrm{MHz}$ to $20 \mathrm{MHz}$
(B) $5 \mathrm{MHz}$ to $10 \mathrm{MHz}$
(C) $100 \mathrm{~Hz}$ to $4 \mathrm{MHz}$
(D) $5 \mathrm{MHz}$ to $20 \mathrm{MHz}$

Nick Johnson

Numerade Educator

Problem 2724

What type of medium is used in optical communication?
(A) guided medium
(B) Unguided medium
(C) Both guided and unguided media
(D) Neither guided nor unguided media

Mirza Aslam Beig

Mirza Aslam Beig

Numerade Educator

Problem 2725

The maximum electron density of a layer of the ionosphere is $9 \times 10^{12} \mathrm{~m}^{-3}$. The critical frequency of this layer is
(A) $9 \mathrm{MHz}$
(B) $6 \mathrm{MHz}$
(C) $27 \mathrm{MHz}$
(D) $3 \mathrm{GHz}$

Mirza Aslam Beig

Mirza Aslam Beig

Numerade Educator

Problem 2726

Which condition is to be satisfied in an AM detector circuit so that the signal corresponds to an envelope of the carrier wave ?
(A) $\mathrm{T}_{\mathrm{C}}<<\mathrm{RC}$
(B) $\mathrm{T}_{\mathrm{c}}>\mathrm{RC}$
(C) $F_{C}<<R C$
(D) $\left(1 / f_{n}\right)<<R C$

Mirza Aslam Beig

Mirza Aslam Beig

Numerade Educator

Problem 2727

The transmission of audio signal in radio broadcasting is type.
(A) ASK
(B) FSK
(C) AM
(D) FM

Mirza Aslam Beig

Mirza Aslam Beig

Numerade Educator

Problem 2728

Iransmission loss per $\mathrm{km}$ in the optical fiber, used presently is,
(A) $20 \mathrm{~dB}$
(B) $2 \mathrm{~dB}$
(C) $0.2 \mathrm{~dB}$
(D) $0.02 \mathrm{~dB}$

Mirza Aslam Beig

Mirza Aslam Beig

Numerade Educator

Problem 2729

In satellite communication $6 \mathrm{GHz}$ frequency is used for and $4 \mathrm{GHz}$ frequency is used for
(A) uplink, down link
(B) down link, up link
(C) modulation, demodulation
(D) demodulation, modulation

Mirza Aslam Beig

Mirza Aslam Beig

Numerade Educator

Problem 2730

Assertion: Microwave communication is preferred over optical communication. Reason: Microwaves provide large number of channels and bandwidth an compared to optical signals.
(A) Both assertion and reason are true and the reason is correct explanation of assertion
(B) Both assertion and reason are true and the reason is not the correct explanation of assertion.
(C) Assertion is true but reason is false.
(D) Both assertion and reason are false.

Mirza Aslam Beig

Mirza Aslam Beig

Numerade Educator

Problem 2731

If a radio receiver amplifies all the signal frequencies equally well, it is said to have high
(A) fidelity
(B) distortion
(C) sensibility
(D) sensitivity

Mirza Aslam Beig

Mirza Aslam Beig

Numerade Educator

Problem 2732

In frequency modulation
(A) the amplitude of modulated wave varies as frequency of carrier wave.
(B) the frequency of modulated wave varies as amplitude of modulating wave.
(C) The amplitude of modulated wave varies as amplitude of carrier wave.
(D) The frequency of modulated wave varies as frequency of modulating wave.

Arpit Gupta

Numerade Educator

Problem 2733

A silicon optical fiber with a care diameter large enough has a core refractive index of $1.50$ and cladding refractive index 1.47. The critical angle at the core cladding interface is
(A) $87.5^{\circ}$
(B) $78.5^{\circ}$
(C) $38.5^{\circ}$
(D) $45^{\circ}$

Mirza Aslam Beig

Mirza Aslam Beig

Numerade Educator

Problem 2734

In satellite communication
(1) The frequency used lies between $5 \mathrm{MHz}$ and $1 \mathrm{MHz}$
(2) The uplink and downlink frequencies are different.
(3) The orbit of geostationary satellite lies in the equatorial plane at an inclination of $0^{\circ}$. In the above statements.
(A) Only 2 and 3 are true
(B) all are true
(C) Only 2 is true
(D) Only 1 and 3 are true

Mirza Aslam Beig

Mirza Aslam Beig

Numerade Educator

Problem 2735

A signal wave of frequency $12 \mathrm{KHz}$ is modulated with a carrier wave of frequency $2.51 \mathrm{MHz}$. The upper and lower side band frequency are respectively.
(A) $2512 \mathrm{~Hz}$ and $2508 \mathrm{KHz}$
(B) $2522 \mathrm{KHz}$ and $2488 \mathrm{KHz}$
(C) $2502 \mathrm{KHz}$ and $2498 \mathrm{KHz}$
(D) $2522 \mathrm{KHz}$ and $2498 \mathrm{KHz}$

Nidhi Singhi

Numerade Educator

Problem 2736

The rms value of electric field of light coming from sun is $720 \mathrm{~N} / \mathrm{c}$. The average total energy density of electromagnetic wave is
(A) $6.37 \times 10^{-9} \mathrm{~J} / \mathrm{m}^{3}$
(B) $4.58 \times 10^{-6} \mathrm{~J} / \mathrm{m}^{3}$
(C) $81.35 \times 10^{-12} \mathrm{~J} / \mathrm{m}^{3}$
(A) $3.3 \times 10^{-3} \mathrm{~J} / \mathrm{m}^{3}$

Khoobchandra Agrawal

Khoobchandra Agrawal

Numerade Educator

Problem 2737

Wave impedance of free space is
(A) Zero
(B) $376.6 \Omega$
(C) $33.6 \Omega$
(D) $3.76 \Omega$

Mirza Aslam Beig

Mirza Aslam Beig

Numerade Educator

Problem 2738

What is the M.U.F (maximum unusable frequency of an electromagnetic wave initial frequency of $20 \mathrm{MHz}$ and incident at an angle of $60^{\circ}$ in ionosphere propagation?
(A) $20 \sqrt{2} \mathrm{MHz}$
(B) $20 \mathrm{MHz}$
(C) $(20 / \sqrt{2}) \mathrm{MHz}$
(D) $40 \mathrm{MHz}$

Mirza Aslam Beig

Mirza Aslam Beig

Numerade Educator

Problem 2739

An insulator used in a transmission line has dielectric constant equal to $0.25$ What is the velocity factor of the transmission line ?
(A) $(4 / 3)$
(B) 2
(C) $(3 / 2)$
(D) 4

Mirza Aslam Beig

Mirza Aslam Beig

Numerade Educator

Problem 2740

What is the working principal of optical fiber?
(A) Refraction
(B) Total internal reflection
(C) Dispersion
(D) Scattering

Mirza Aslam Beig

Mirza Aslam Beig

Numerade Educator

Problem 2741

For efficient transmission of a $100 \mathrm{MHz}$ frequency wave, the minimum length of an antenna should be
(A) $3 \mathrm{~m}$
(B) $(3 / 4) \mathrm{m}$
(C) $10 \mathrm{~m}$
(D) $100 \mathrm{~m}$

Mirza Aslam Beig

Mirza Aslam Beig

Numerade Educator

Problem 2742

A photo director area light of wavelength $1400 \mathrm{~nm}$ Band gap of the Semiconductor used in the photo detector is $\left(\mathrm{h}=6.63 \times 10^{-34} \mathrm{JS} ; \mathrm{C}=3 \times 10^{8} \mathrm{~m} / \mathrm{s}\right)$
(A) $0.7 \mathrm{eV}$
(B) $1 \mathrm{eV}$
(C) $2 \mathrm{eV}$
(D) $2.5 \mathrm{eV}$

Mirza Aslam Beig

Mirza Aslam Beig

Numerade Educator

Problem 2743

In modulation process radio signal is called
(A) modulating wave
(B) Carrier wave
(C) modulated wave
(D) transmitting wave

Mirza Aslam Beig

Mirza Aslam Beig

Numerade Educator

Problem 2744

Tank Circuit Contains 1 nf capacitor and 10 microhenry inductor What is the carrier frequency generated by it?
(A) $1629 \mathrm{KHz}$
(B) $1592 \mathrm{KHz}$
(C) $1582 \mathrm{MHz}$
(D) $156.2 \mathrm{KHz}$

Mirza Aslam Beig

Mirza Aslam Beig

Numerade Educator

Problem 2745

The effective power radiated by an antenna varies
(A) inversely as the length of antenna
(B) inversely as the square of the length of the antenna
(C) directly as the length of antenna
(D) directly as the square of the length of the antenna

Mirza Aslam Beig

Mirza Aslam Beig

Numerade Educator

Problem 2746

A $1000 \mathrm{KHz}$ carrier is modulated with $800 \mathrm{~Hz}$ audio signals. What are the frequencies of first pair side band?
(A) $1000 \mathrm{KHz}$ and $800 \mathrm{~Hz}$
(B) $800 \mathrm{~Hz}$ and $999.2 \mathrm{KHz}$
(C) $1000.8 \mathrm{KHz}$ and $999.2 \mathrm{KHz}$
(D) $1000.8 \mathrm{KHz}$ and $1000 \mathrm{KHz}$

Mirza Aslam Beig

Mirza Aslam Beig

Numerade Educator

Problem 2747

The critical frequency of Flayer is $50 \mathrm{MHz}$ when angle of incidence is $74^{\circ}$. What is the maximum unable frequency?
(A) $181.5 \mathrm{MHz}$
(B) $191.5 \mathrm{MHz}$
(C) $199.5 \mathrm{MHz}$
(D) $171.5 \mathrm{MHz}$

Mirza Aslam Beig

Mirza Aslam Beig

Numerade Educator

Problem 2748

The velocity of e.m. waves in a medium is $2.5 \times 10^{8} \mathrm{~ms}^{-1}$. what is the dielectric constant of the medium?
(A) $1.2$
(B) $1.44$
(C) $0.69$
(D) $1.6$

Mirza Aslam Beig

Mirza Aslam Beig

Numerade Educator

Problem 2749

How long will it take to transmit the information $30 \mathrm{~km}$ away in space?
(A) $0.1 \mathrm{~ms}$
(B) $0.1 \mu \mathrm{s}$
(C) $0.1 \mathrm{~ns}$
(D) $0.1 \mathrm{ps}$

Mirza Aslam Beig

Mirza Aslam Beig

Numerade Educator

Problem 2750

What is the velocity of electromagnetic wave in a good conductor ?
(A) $3 \times 10^{8} \mathrm{~m} / \mathrm{s}$
(B) more than $3 \times 10^{8} \mathrm{~m} / \mathrm{s}$
(C) High
(D) Very low

Mirza Aslam Beig

Mirza Aslam Beig

Numerade Educator

Problem 2751

If ' $\mathrm{fm}^{\prime}$ is the modulation frequency in FM the modulation index is proportional to
(A) $\mathrm{fm}$
(B) $\mathrm{f}_{\mathrm{m}}^{2}$
(C) $\left(1 / \mathrm{f}_{\mathrm{m}}\right)$
(D) $\left(1 / \mathrm{f}_{\mathrm{m}}^{2}\right)$

Mirza Aslam Beig

Mirza Aslam Beig

Numerade Educator

Problem 2752

For $100 \%$ modulation, What is the value of minimum amplitude $\left(E_{\min }\right)$ of the modulated wave?
(A) Zero
(B) 1
(C) 2
(D) 3

Mirza Aslam Beig

Mirza Aslam Beig

Numerade Educator

Problem 2753

When electromagnetic waves enter the ionised layer of ionosphere, the relative permitting of the ionised layer
(A) remain constant
(B) appears to decrease
(C) appears to increase
(D) changer randomly

Mirza Aslam Beig

Mirza Aslam Beig

Numerade Educator

Problem 2754

IN which of the following media the wave propagation occurs with out attenuation?
(A) Conductor
(B) perfect dielectric medium
(C) Semi conductor
(D) None of the above

Mirza Aslam Beig

Mirza Aslam Beig

Numerade Educator

Problem 2755

The step index fiber has a relative refractive index difference of $0.86 \%$ what is the critical angle at the core cladding interface?
(A) $28.4^{\circ}$
(B) $82.4^{\circ}$
(C) $24.8^{\circ}$
(D) $75.6^{\circ}$

Mirza Aslam Beig

Mirza Aslam Beig

Numerade Educator

Problem 2756

A silicon optical fiber has a core refractive index of $1.50$ and a cladding refractive index $1.47$ what is the numerical aperture of the fiber?
(A) $0.90$
(B) $0.60$
(C) $0.45$
(D) $0.30$

Mirza Aslam Beig

Mirza Aslam Beig

Numerade Educator

Problem 2757

Which of the following alternative is not natural Noise ?
(A) Thunder of light
(B) Radiation coming from sun.
(C) Radiation coming from stars
(D) Radiation produced by flickering of tube light

Mirza Aslam Beig

Mirza Aslam Beig

Numerade Educator

Problem 2758

In optical fiber communication, the APD semi conductor device is used
(A) to convert radio signal into optical signal.
(B) to obtain intensity modulated signal
(C) to covert optical signal into electrical signal
(D) to covert optical signal into radio signal.

Mirza Aslam Beig

Mirza Aslam Beig

Numerade Educator

Problem 2759

For AM, value of modulation index should be always
$(\mathrm{A})<1$
(B) $=1$
(C) $>1$
(D) 0

Mirza Aslam Beig

Mirza Aslam Beig

Numerade Educator

Problem 2760

Refractive index of ionosphere is
(A) one
(B) more than one
(C) less than one
(D) Zero
Copyright ( C StemEZ.com. All rights reserved.

Mirza Aslam Beig

Mirza Aslam Beig

Numerade Educator