Question 1: Palette 1/82

JEE Mains 2023 MCQ

The height of transmitting antenna is $180 \mathrm{~m}$ and the height of the receiving antenna is $245 \mathrm{~m}$. The maximum distance between them for satisfactory communication in line of sight will be :

(given $\mathrm{R}=6400 \mathrm{~km})$

A

$104 \mathrm{~km}$

B

$56 \mathrm{~km}$

C

$48 \mathrm{~km}$

D

$96 \mathrm{~km}$

Question 2: Palette 2/82

JEE Mains 2023 MCQ

To radiate EM signal of wavelength $\lambda$ with high efficiency, the antennas should have a minimum size equal to:

A

$\frac{\lambda}{2}$

B

$\lambda$

C

$\frac{\lambda}{4}$

D

$2 \lambda$

Question 3: Palette 3/82

JEE Mains 2023 MCQ

Match List - I with List - II

	List - I (Layer of atmosphere)		List - II (Approximate height over earth's surface)
(A)	$\mathrm{F_1}$ - Layer	(I)	10 km
(B)	$\mathrm{D}$ - Layer	(II)	170 - 190 km
(C)	Troposphere	(III)	100 km
(D)	$\mathrm{E}$ - Layer	(IV)	65 - 75 km

Choose the correct answer from the options given below:

A

A - II, B - IV, C - III, D - I

B

A - II, B-I, C - IV, D - III

C

A - II, B - IV, C - I, D - III

D

A - III, B - IV, C - I, D - II

Question 4: Palette 4/82

JEE Mains 2023 MCQ

The amplitude of $15 \sin (1000 \pi \mathrm{t})$ is modulated by $10 \sin (4 \pi \mathrm{t})$ signal. The amplitude modulated signal contains frequencies of

A. $500 \mathrm{~Hz}$

B. $2 \mathrm{~Hz}$

C. $250 \mathrm{~Hz}$

D. $498 \mathrm{~Hz}$

E. $502 \mathrm{~Hz}$

Choose the correct answer from the options given below:

A

A and C only

B

A and B only

C

A and D only

D

A, D and E only

Question 5: Palette 5/82

JEE Mains 2023 MCQ

In satellite communication, the uplink frequency band used is :

A

$3.7-4.2 \mathrm{~GHz}$

B

$5.925-6.425 \mathrm{~GHz}$

C

$76-88 \mathrm{~MHz}$

D

$420-890 \mathrm{~MHz}$

Question 6: Palette 6/82

JEE Mains 2023 MCQ

A transmitting antenna is kept on the surface of the earth. The minimum height of receiving antenna required to receive the signal in line of sight at $4 \mathrm{~km}$ distance from it is $x \times 10^{-2} \mathrm{~m}$. The value of $x$ is __________.

(Let, radius of earth $\mathrm{R}=6400 \mathrm{~km}$ )

A

1.25

B

125

C

1250

D

12.5

Question 7: Palette 7/82

JEE Mains 2023 MCQ

A message signal of frequency $3 ~\mathrm{kHz}$ is used to modulate a carrier signal of frequency $1.5 ~\mathrm{MHz}$. The bandwidth of the amplitude modulated wave is

A

$6 ~\mathrm{MHz}$

B

$6 ~\mathrm{kHz}$

C

$3 ~\mathrm{MHz}$

D

$3 ~\mathrm{kHz}$

Question 8: Palette 8/82

JEE Mains 2023 MCQ

A carrier wave of amplitude 15 V is modulated by a sinusoidal base band signal of magnitude 3 V. The ratio of maximum amplitude to minimum amplitude in an amplitude modulated wave is

A

1

B

5

C

2

D

$\frac{3}{2}$

Question 9: Palette 9/82

JEE Mains 2023 MCQ

The power radiated from a linear antenna of length $l$ is proportional to

(Given, $\lambda=$ Wavelength of wave):

A

$\left(\frac{l}{\lambda}\right)^{2}$

B

$\frac{l}{\lambda^{2}}$

C

$\frac{l^{2}}{\lambda}$

D

$\frac{l}{\lambda}$

Question 10: Palette 10/82

JEE Mains 2023 MCQ

A TV transmitting antenna is $98 \mathrm{~m}$ high and the receiving antenna is at the ground level. If the radius of the earth is $6400 \mathrm{~km}$, the surface area covered by the transmitting antenna is approximately:

A

$4868 \mathrm{~km}^{2}$

B

$1240 \mathrm{~km}^{2}$

C

$3942 \mathrm{~km}^{2}$

D

$1549 \mathrm{~km}^{2}$

Question 11: Palette 11/82

JEE Mains 2023 MCQ

For an amplitude modulated wave the minimum amplitude is $3 \mathrm{~V}$, while the modulation index is $60 \%$. The maximum amplitude of the modulated wave is:

A

5 V

B

12 V

C

10 V

D

15 V

Question 12: Palette 12/82

JEE Mains 2023 MCQ

By what percentage will the transmission range of a TV tower be affected when the height of the tower is increased by $21 \%$ ?

A

12%

B

15%

C

10%

D

14%

Question 13: Palette 13/82

JEE Mains 2023 MCQ

In an amplitude modulation, a modulating signal having amplitude of X Volt is superimposed with a carrier signal of amplitude Y Volt in first case. Then, in second case, the same modulating signal is superimposed with different carrier signal of amplitude 2Y Volt. The ratio of modulation index in the two cases respectively will be :

A

2 : 1

B

1 : 1

C

4 : 1

D

1 : 2

Question 14: Palette 14/82

JEE Mains 2023 MCQ

Which of the following frequencies does not belong to FM broadcast ?

A

$106 ~\mathrm{MHz}$

B

$89 ~\mathrm{MHz}$

C

$64 ~\mathrm{MHz}$

D

$99 ~\mathrm{MHz}$

Question 15: Palette 15/82

JEE Mains 2023 MCQ

Given below are two statements :

Statement I : For transmitting a signal, size of antenna ( $l$ ) should be comparable to wavelength of signal (at least $l=\frac{\lambda}{4}$ in dimension)

Statement II: In amplitude modulation, amplitude of carrier wave remains constant (unchanged).

In the light of the above statements, choose the most appropriate answer from the options given below

A

Statement I is incorrect but Statement II is correct

B

Both Statement I and Statement II are correct

C

Both Statement I and Statement II are incorrect

D

Statement I is correct but Statement II is incorrect

Question 16: Palette 16/82

JEE Mains 2023 MCQ

The amplitude of $15 \sin (1000 \pi \mathrm{t})$ is modulated by $10 \sin (4 \pi \mathrm{t})$ signal. The amplitude modulated signal contains frequency (ies) of

A. $500 \mathrm{~Hz}$

B. $2 \mathrm{~Hz}$

C. $250 \mathrm{~Hz}$

D. $498 \mathrm{~Hz}$

E. $502 \mathrm{~Hz}$

Choose the correct answer from the options given below:

A

B only

B

A only

C

A, D and E only

D

A and B only

Question 17: Palette 17/82

JEE Mains 2023 MCQ

Match List I with List II:

List I	List II
A. Attenuation	I. Combination of a receiver and transmitter.
B. Transducer	II. process of retrieval of information from the carrier wave at receiver
C. Demodulation	III. converts one form of energy into another
D. quad Repeater	IV. Loss of strength of a signal while propagating through a medium.

Choose the correct answer from the options given below:

A

A-I, B-II, C-III, D-IV

B

A-IV, B-III, C-I, D-II

C

A-IV, B-III, C-II, D-I

D

A-II, B-III, C-IV, D-I

Question 18: Palette 18/82

JEE Mains 2023 MCQ

A sinusoidal carrier voltage is amplitude modulated. The resultant amplitude modulated wave has maximum and minimum amplitude of $120 \mathrm{~V}$ and $80 \mathrm{~V}$ respectively. The amplitude of each sideband is :

A

15 V

B

20 V

C

5 V

D

10 V

Question 19: Palette 19/82

JEE Mains 2023 MCQ

The modulation index for an A.M. wave having maximum and minimum peak-to-peak voltages of 14 mV and 6 mV respectively is-

A

0.4

B

0.6

C

1.4

D

0.2

Question 20: Palette 20/82

JEE Mains 2023 MCQ

If the height of transmitting and receiving antennas are 80 m each, the maximum line of sight distance will be:

Given : Earth's radius $=6.4\times10^6$ m

A

28 km

B

64 km

C

32 km

D

36 km

Question 21: Palette 21/82

JEE Mains 2023 MCQ

Match List I with List II

	List I		List II
A.	Troposphere	I.	Approximate 65-75 km over Earth's surface
B.	E-Part of Stratosphere	II.	Approximate 300 km over Earth's surface
C.	F$_2$-Part of Thermosphere	III.	Approximate 10 km over Earth's surface
D.	D-Part of Stratosphere	IV.	Approximate 100 km over Earth's surface

Choose the correct answer from the options given below :

A

A-III, B-IV, C-II, D-I

B

A-III, B-II, C-I, D-IV

C

A-I, B-IV, C-III, D-II

D

A-I, B-II, C-IV, D-III

Question 22: Palette 22/82

JEE Mains 2023 MCQ

A message signal of frequency 5 kHz is used to modulate a carrier signal of frequency 2 MHz. The bandwidth for amplitude modulation is :

A

10 kHz

B

2.5 kHz

C

20 kHz

D

5 kHz

Question 23: Palette 23/82

JEE Mains 2023 MCQ

Match List I with List II

	List-I		List-II
A.	AM Broadcast	I.	88-108 MHz
B.	FM Broadcast	II.	540-1600 kHz
C.	Television	III.	3.7-4.2 GHz
D.	Satellite Communication	IV.	54MHz - 890MHz

Choose the correct answer from the options given below :

A

A-IV, B-III, C-I, D-II

B

A-II, B-I, C-IV, D-III

C

A-I, B-III, C-II, D-IV

D

A-II, B-III, C-I, D-IV

Question 24: Palette 24/82

JEE Mains 2023 MCQ

A modulating signal is a square wave, as shown in the figure.

If the carrier wave is given as $\mathrm{c(t) = 2\sin(8\pi t)}$ volts, the modulation index is :

A

$\frac{1}{3}$

B

1

C

$\frac{1}{4}$

D

$\frac{1}{2}$

Question 25: Palette 25/82

JEE Mains 2022 MCQ

Find the modulation index of an AM wave having $8 \mathrm{~V}$ variation where maximum amplitude of the AM wave is $9 \mathrm{~V}$.

A

0.8

B

0.5

C

0.2

D

0.1

Question 26: Palette 26/82

JEE Mains 2022 MCQ

A FM Broadcast transmitter, using modulating signal of frequency 20 kHz has a deviation ratio of 10. The Bandwidth required for transmission is :

A

220 kHz

B

180 kHz

C

360 kHz

D

440 khz

Question 27: Palette 27/82

JEE Mains 2022 MCQ

In the case of amplitude modulation to avoid distortion the modulation index $(\mu)$ should be :

A

$\mu \leq 1$

B

$\mu \geq 1$

C

$\mu = 2$

D

$\mu = 0$

Question 28: Palette 28/82

JEE Mains 2022 MCQ

A square wave of the modulating signal is shown in the figure. The carrier wave is given by $C(t)=5 \sin (8 \pi t)$ Volt. The modulation index is :

A

0.2

B

0.1

C

0.3

D

0.4

Question 29: Palette 29/82

JEE Mains 2022 MCQ

At a particular station, the TV transmission tower has a height of 100 m. To triple its coverage range, height of the tower should be increased to

A

200 m

B

300 m

C

600 m

D

900 m

Question 30: Palette 30/82

JEE Mains 2022 MCQ

The maximum and minimum voltage of an amplitude modulated signal are $60 \mathrm{~V}$ and $20 \mathrm{~V}$ respectively. The percentage modulation index will be :

A

0.5%

B

50%

C

2%

D

30%

Question 31: Palette 31/82

JEE Mains 2022 MCQ

A radio can tune to any station in $6 \,\mathrm{MHz}$ to $10 \,\mathrm{MHz}$ band. The value of corresponding wavelength bandwidth will be :

A

4 m

B

20 m

C

30 m

D

50 m

Question 32: Palette 32/82

JEE Mains 2022 MCQ

In AM modulation, a signal is modulated on a carrier wave such that maximum and minimum amplitudes are found to be 6 V and 2 V respectively. The modulation index is :

A

100%

B

80%

C

60%

D

50%

Question 33: Palette 33/82

JEE Mains 2022 MCQ

A speech signal given by 11 sin(2200 $\pi$t) V is used for amplitude modulation with a carrier signal given by 44 sin(6600 $\pi$t) V. The minimum amplitude of modulated wave will be :

A

33 V

B

55 V

C

8.25 V

D

13.75 V

Question 34: Palette 34/82

JEE Mains 2022 MCQ

The TV transmission tower at a particular station has a height of 125 m. For doubling the coverage of its range, the height of the tower should be increased by

A

125 m

B

250 m

C

375 m

D

500 m

Question 35: Palette 35/82

JEE Mains 2022 MCQ

Only 2% of the optical source frequency is the available channel bandwidth for an optical communicating system operating at 1000 nm. If an audio signal requires a bandwidth of 8 kHz, how many channels can be accommodated for transmission :

A

375 $\times$ 10⁷

B

75 $\times$ 10⁷

C

375 $\times$ 10⁸

D

75 $\times$ 10⁹

Question 36: Palette 36/82

JEE Mains 2022 MCQ

Amplitude modulated wave is represented by ${V_{AM}} = 10\,[1 + 0.4\cos (2\pi \times {10^4}t)]\cos (2\pi \times {10^7}t)$. The total bandwidth of the amplitude modulated wave is :

A

10 kHz

B

20 MHz

C

20 kHz

D

10 MHz

Question 37: Palette 37/82

JEE Mains 2022 MCQ

Match List-I with List-II

	List-I		List-II
(A)	Television signal	(I)	03 KHz
(B)	Radio signal	(II)	20 KHz
(C)	High Quality Music	(III)	02 MHz
(D)	Human speech	(IV)	06 MHz

A

A-I, B-II, C-III, D-IV

B

A-IV, B-III, C-I, D-II

C

A-IV, B-III, C-II, D-I

D

A-I, B-II, C-IV, D-III

Question 38: Palette 38/82

JEE Mains 2022 MCQ

We do not transmit low frequency signal to long distances because-

(a) The size of the antenna should be comparable to signal wavelength which is unreal solution for a signal of longer wavelength.

(b) Effective power radiated by a long wavelength baseband signal would be high.

(c) We want to avoid mixing up signals transmitted by different transmitter simultaneously.

(d) Low frequency signal can be sent to long distances by superimposing with a high frequency wave as well.

Therefore, the most suitable option will be :

A

All statements are true

B

(a), (b) and (c) are true only

C

(a), (c) and (d) are true only

D

(b), (c) and (d) are true only

Question 39: Palette 39/82

JEE Mains 2022 MCQ

A sinusoidal wave y(t) = 40sin(10 $\times$ 10⁶ $\pi$t) is amplitude modulated by another sinusoidal wave x(t) = 20sin (1000 $\pi$t). The amplitude of minimum frequency component of modulated signal is :

A

0.5

B

0.25

C

20

D

10

Question 40: Palette 40/82

JEE Mains 2022 MCQ

Choose the correct statement for amplitude modulation :

A

Amplitude of modulating signal is varied in accordance with the information signal.

B

Amplitude of modulated signal is varied in accordance with the information signal.

C

Amplitude of carrier signal is varied in accordance with the information signal.

D

Amplitude of modulated signal is varied in accordance with the modulating signal.

Question 41: Palette 41/82

JEE Mains 2022 MCQ

Match List I with List II

	List - I		List -II
A.	Facsimile	I.	Static Document Image
B.	Guided media Channel	II.	Local Broadcast Radio
C.	Frequency Modulation	III.	Rectangular wave
D.	Digital Signal	IV.	Optical Fiber

Choose the correct answer from the following options:

A

A-IV, B-III, C-II, D-I

B

A-I, B-IV, C-II, D-III

C

A-IV, B-II, C-III, D-I

D

A-I, B-II, C-III, D-IV

Question 42: Palette 42/82

JEE Mains 2022 MCQ

A signal of 100 THz frequency can be transmitted with maximum efficiency by :

A

Coaxial cable

B

Optical fibre

C

Twisted pair of copper wires

D

Water

Question 43: Palette 43/82

JEE Mains 2022 MCQ

A baseband signal of 3.5 MHz frequency is modulated with a carrier signal of 3.5 GHz frequency using amplitude modulation method. What should be the minimum size of antenna required to transmit the modulated signal?

A

42.8 m

B

42.8 mm

C

21.4 mm

D

21.4 m

Question 44: Palette 44/82

JEE Mains 2021 MCQ

An antenna is mounted on a 400 m tall building. What will be the wavelength of signal that can be radiated effectively by the transmission tower upto a range of 44 km?

A

37.8 m

B

605 m

C

75.6 m

D

302 m

Question 45: Palette 45/82

JEE Mains 2021 MCQ

A transmitting antenna at top of a tower has a height of 50 m and the height of receiving antenna is 80 m. What is range of communication for Line of Sight (LoS) mode?

[use radius of earth = 6400 km]

A

45.5 km

B

80.2 km

C

144.1 km

D

57.28 km

Question 46: Palette 46/82

JEE Mains 2021 MCQ

In amplitude modulation, the message signal

V_m(t) = 10 sin (2$\pi$ $\times$ 10⁵t) volts and

Carrier signal

V_C(t) = 20 sin(2$\pi$ $\times$ 10⁷ t) volts

The modulated signal now contains the message signal with lower side band and upper side band frequency, therefore the bandwidth of modulated signal is $\alpha$ kHz. The value of $\alpha$ is :

A

200 kHz

B

50 kHz

C

100 kHz

D

0

Question 47: Palette 47/82

JEE Mains 2021 MCQ

What should be the height of transmitting antenna and the population covered if the television telecast is to cover a radius of 150 km? The average population density around the tower is 2000/km² and the value of R_e = 6.5 $\times$ 10⁶ m.

A

Height = 1241 m

Population covered = 7 $\times$ 10⁵

B

Height = 1731 m

Population covered = 1413 $\times$ 10⁵

C

Height = 1800 m

Population covered = 1413 $\times$ 10⁸

D

Height = 1600 m

Population covered = 2 $\times$ 10⁵

Question 48: Palette 48/82

JEE Mains 2021 MCQ

Match List - I with List - II.

List - I

(a) 10 km height over earth's surface

(b) 70 km height over earth's surface

(c) 180 km height over earth's surface

(d) 270 km height over earth's surface

List - II

(i) Thermosphere

(ii) Mesosphere

(iii) Stratosphere

(iv) Troposphere

A

(a)-(iv), (b)-(iii), (c)-(ii), (d)-(i)

B

(a)-(i), (b)-(iv), (c)-(iii), (d)-(ii)

C

(a)-(iii), (b)-(ii), (c)-(i), (d)-(iv)

D

(a)-(ii), (b)-(i), (c)-(iv), (d)-(iii)

Question 49: Palette 49/82

JEE Mains 2021 MCQ

A carrier signal C(t) = 25 sin(2.512 $\times$ 10¹⁰t) is amplitude modulated by a message signal m(t) = 5 sin(1.57 $\times$ 10⁸t) and transmitted through an antenna. What will be the bandwidth of the modulated signal?

A

50 MHz

B

8 GHz

C

1987.5 MHz

D

2.01 GHz

Question 50: Palette 50/82

JEE Mains 2021 MCQ

Two identical antennas mounted on identical towers are separated from each other by a distance of 45 km. What should nearly be the minimum height of receiving antenna to receive the signals in line of sight? (Assume radius of earth is 6400 km)

A

158.2 m

B

79.1 m

C

19.77 m

D

39.55 m

Question 51: Palette 51/82

JEE Mains 2021 MCQ

A 25 m long antenna is mounted on an antenna tower. The height of the antenna tower is 75 m. The wavelength (in meter) of the signal transmitted by this antenna would be :

A

200

B

400

C

100

D

300

Question 52: Palette 52/82

JEE Mains 2021 MCQ

If a message signal of frequency 'f_m' is amplitude modulated with a carrier signal of frequency 'f_c' and radiated through an antenna, the wavelength of the corresponding signal in air is :

A

${c \over {{f_c} + {f_m}}}$

B

${c \over {{f_c}}}$

C

${c \over {{f_c} - {f_m}}}$

D

${c \over {{f_m}}}$

Question 53: Palette 53/82

JEE Mains 2021 MCQ

Given below are two statements :

Statement I : A speech signal of 2 kHz is used to modulate a carrier signal of 1 MHz. The bandwidth requirement for the signal is 4 kHz.

Statement II : The side band frequencies are 1002 kHz and 998 kHz.

In the light of the above statements, choose the correct answer from the options given below :

A

Statement I is false but Statement II is true

B

Both Statement I and Statement II are false

C

Statement I is true but Statement II is false

D

Both Statement I and Statement II are true

Question 54: Palette 54/82

JEE Mains 2020 MCQ

An amplitude modulated wave is represented by the expression
v_m = 5(1 + 0.6 cos 6280t) sin(211 × 10⁴ t) volts
The minimum and maximum amplitudes of the amplitude modulated wave are, respectively

A

${3 \over 2}$ V, 5 V

B

${5 \over 2}$ V, 8 V

C

5 V, 8 V

D

3 V, 5 V

Question 55: Palette 55/82

JEE Mains 2019 MCQ

In an amplitude modulator circuit, the carrier wave is given by, C(t) = 4 sin(20000 $\pi $t) while modulating signal is given by, m(t) = 2 sin (2000 $\pi $t). The values of modulation index and lower side band frequency are :

A

0.3 and 9 kHz

B

0.5 and 10 kHz

C

0.4 and 10 kHz

D

0.5 and 9 kHz

Question 56: Palette 56/82

JEE Mains 2019 MCQ

A message signal of frequency 100 MHz and peak voltage 100 V is used to execute amplitude modulation on a carrier wave of frequency 300 GHz and peak voltage 400 V. The modulation index and difference between the two side band frequencies are :

A

0.25; 1 × 10⁸ Hz

B

4; 2 × 10⁸ Hz

C

4; 1 × 10⁸ Hz

D

0.25; 2 × 10⁸ Hz

Question 57: Palette 57/82

JEE Mains 2019 MCQ

Given below in the the left column are different modes of communication using the kinds of waves given the right column.

A	Optical Fibre communication	P	Ultrasound
B	Radar	Q	Infrared Light
C	Sonar	R	Microwaves
D	Mobile Phones	S	Radio Waves

A

A-Q, B-S, C-R, D-P

B

A-Q, B-S, C-P, D-R

C

A-S, B-Q, C-R, D-P

D

A-R, B-P, C-S, D-Q

Question 58: Palette 58/82

JEE Mains 2019 MCQ

The physical sizes of the transmitter and receiver antenna in a communication system are :-

A

proportional to carrier frequency

B

inversely proportional to carrier frequency

C

inversely proportional to modulation frequency

D

independent of both carrier and modulation frequency

Question 59: Palette 59/82

JEE Mains 2019 MCQ

A signal Acoswt is transmitted using v₀ sin $\omega $₀t as carrier wave. The correct amplitude modulated (AM) signal is

A

v₀ sin $\omega $₀t + Acos$\omega $t

B

(v₀ + A)cos$\omega $t sin$\omega $₀ t

C

v₀ sin[$\omega $₀ (1+ 0.01Asin$\omega $t)t]

D

${v_0}\sin {\omega _0}t + {{\rm A} \over 2}\sin ({\omega _0} - \omega )t + {A \over 2}\sin ({\omega _0} + \omega )t$

Question 60: Palette 60/82

JEE Mains 2019 MCQ

In a line of sight radio communication, a distance of about 50 km is kept between the transmitting and receiving antennas. If the height of the receiving antenna is 70m, then the minimum height of the transmitting antenna should be :
(Radius of the Earth = 6.4 × 10⁶ m).

A

40 m

B

20 m

C

51 m

D

32 m

Question 61: Palette 61/82

JEE Mains 2019 MCQ

The wavelength of the carrier waves in a modern optical fiber communication network is close to :

A

1500 nm

B

2400 nm

C

600 nm

D

900 nm

Question 62: Palette 62/82

JEE Mains 2019 MCQ

To double the covering range of a TV transmittion tower, its height should be multiplied by :

A

4

B

2

C

$\sqrt 2 $

D

${1 \over {\sqrt 2 }}$

Question 63: Palette 63/82

JEE Mains 2019 MCQ

A 100 V carrier wave is made to vary between 160 V and 40 V by a modulating signal. What is the modulation index ?

A

0.5

B

0.6

C

0.4

D

0.3

Question 64: Palette 64/82

JEE Mains 2019 MCQ

An amplitude modulated signal is plotted below :



Which one of the following best describes the above signal ?

A

(1 + 9sin (2$\pi $ $ \times $ 10⁴ t)) sin(2.5$\pi $ $ \times $ 10⁵t) V

B

(9 + sin (4$\pi $ $ \times $ 10⁴ t)) sin(5$\pi $ $ \times $ 10⁵t) V

C

(9 + sin (2$\pi $ $ \times $ 10⁴ t)) sin(2.5$\pi $ $ \times $ 10⁵t) V

D

(9 + sin (2.5$\pi $ $ \times $ 10⁴ t)) sin(2$\pi $ $ \times $ 10⁴t) V

Question 65: Palette 65/82

JEE Mains 2019 MCQ

An amplitude modulated signal is given by V(t) = 10[1 + 0.3cos(2.2 $ \times $ 10⁴ t)] sin(5.5 $ \times $ 10⁵ t). Here t is in seconds. The sideband frequencies (in kHz) are, [Given $\pi $ = 22/7]

A

892.5 and 857.5

B

89.25 and 85.75

C

1785 and 1715

D

178.5 and 171.5

Question 66: Palette 66/82

JEE Mains 2019 MCQ

The modulation frequency of an AM radio station is 250 kHz, which is 10% of the carrier wave. If another AM station approaches you for license what broadcast frequency will you allot ?

A

2900 kHz

B

2750 kHz

C

2250 kHz

D

2000 kz

Question 67: Palette 67/82

JEE Mains 2019 MCQ

A TV transmission tower has a height of 140 m and the height of the receiving antenna is 40 m. What is the maximum distance upto which signals can be broadcasted from this tower is LOS (Line of Sight) mode ? (Given : radius of earth = 6.4 × 10⁶ m).

A

40 km

B

65 km

C

48 km

D

80 km

Question 68: Palette 68/82

JEE Mains 2019 MCQ

In a communication system operating at wavelength 800 nm, only one percent of source frequency is available as signal bandwith. The number of channels accomodated for transmitting TV signals of band width 6 MHz are (Take velocity of light c = 3 $ \times $ 10⁸m/s, h = 6.6 $ \times $ 10^$-$34 J-s)

A

3.75 $ \times $ 10⁶

B

3.86 $ \times $ 10⁶

C

6.25 $ \times $ 10⁵

D

4.87 $ \times $ 10⁵

Question 69: Palette 69/82

JEE Mains 2018 MCQ

A carrier wave of peak voltage 14 V is used for transmitting a message signal. The peak voltage of modulating signal given to achieve a modulation index of 80% will be :

A

7 V

B

28 V

C

11.2 V

D

22.4 V

Question 70: Palette 70/82

JEE Mains 2018 MCQ

A telephonic communication service is working at carrier frequency of 10 GHz. Only 10% of it is utilized for transmission. How many telephonic channels can be transmitted simultaneously if each channel requires a bandwidth of 5 kHz ?

A

2 $\times$ 10⁶

B

2 $\times$ 10³

C

2 $\times$ 10⁵

D

2 $\times$ 10⁴

Question 71: Palette 71/82

JEE Mains 2018 MCQ

The carrier frequency of a transmitter is provided by a tank circuit of a coil of inductance 49 $\mu $H and a capacitance of 2.5 nF. It is modulated by an audio signal of $12$ $kHz.$ The frequency range occupied by the side bands is :

A

13482 kHz $-$ 13494 kHz

B

442 kHz $-$ 466 kHz

C

63 kHz $-$ 75 kHz

D

18 kHz $-$ 30 kHz

Question 72: Palette 72/82

JEE Mains 2018 MCQ

The number of amplitude modulted broadcast stations that can be accomodated in a $300$ $kHz$ band width for the highest modulating frequency $15$ $kHz$ will be :

A

$20$

B

$15$

C

$10$

D

$8$

Question 73: Palette 73/82

JEE Mains 2017 MCQ

A signal is to be transmitted through a wave of wavelength $\lambda $, using a linear antenna. The length l of the antenna and effective power radiated P_eff will be given respectively as :

(K is a constant of proportionality)

A

$\lambda $, P_eff = K $\left( {{1 \over \lambda }} \right)$²

B

${{\lambda \over 8}}$, P_eff = K $\left( {{1 \over \lambda }} \right)$

C

${{\lambda \over 16}}$, P_eff = K $\left( {{1 \over \lambda }} \right)$³

D

${{\lambda \over 5}}$, P_eff = K $\left( {{1 \over \lambda }} \right)$${\left( {{1 \over \lambda }} \right)^{{1 \over 2}}}$

Question 74: Palette 74/82

JEE Mains 2017 MCQ

A signal of frequency 20 kHz and peak voltage of 5 Volt is used to modulate a carrier wave of frequency 1.2 MHz and peak voltage 25 Volts. Choose the correct statement.

A

Modulation index = 5, side frequency bands are at 1400 kHz and 1000 kHz

B

Modulation index = 5, side frequency bands are at 21.2 kHz and 18.8 kHz

C

Modulation index = 0.8, side frequency bands are at 1180 kHz and 1220 kHz

D

Modulation index = 0.2, side frequency bands are at 1220 kHz and 1180 kHz

Question 75: Palette 75/82

JEE Mains 2017 MCQ

In amplitude modulation, sinusoidal carrier frequency used is denoted by ${\omega _c}$ and the signal frequency is denoted by ${\omega _m}$. The bandwidth ($\Delta {\omega _m}$) of the signal is such that $\Delta {\omega _m}$ < < $\omega _c$. Which of the following frequencies is not contained in the modulated wave?

A

${\omega _m}$

B

${\omega _c}$

C

${\omega _m}$ + ${\omega _c}$

D

${\omega _c}$ - ${\omega _m}$

Question 76: Palette 76/82

JEE Mains 2016 MCQ

A modulated signal C_m(t) has the form C_m(t) = 30 sin 300 $\pi $t + 10 (cos 200 $\pi $t −cos 400 $\pi $t). The carrier frequency c, the modulating frequency (message frequency) f_{$\omega $}, and the modulation index $\mu $ are respectively given by :

A

f_c = 200 Hz; f_{$\omega $} = 50 Hz; $\mu $ = ${1 \over 2}$

B

f_c = 150 Hz; f_{$\omega $} = 50 Hz; $\mu $ = ${2 \over 3}$

C

f_c = 150 Hz; f_{$\omega $} = 30 Hz; $\mu $ = ${1 \over 3}$

D

f_c = 200 Hz; f_{$\omega $} = 30 Hz; $\mu $ = ${1 \over 2}$

Question 77: Palette 77/82

JEE Mains 2016 MCQ

An audio signal consists of two distinct sounds : one a human speech signal in the frequency band of 200 Hz to 2700 Hz, while the other is a high frequency music signal in the frequency band of 10200 Hz to 15200 Hz. The ratio of the AM signal bandwidth required to send both the signals together to the AM signal bandwidth required to send just the human speech is :

A

3

B

5

C

6

D

2

Question 78: Palette 78/82

JEE Mains 2016 MCQ

Choose the correct statement :

A

In amplitude modulation the amplitude of the high frequency carrier wave is make to vary in proportion to the amplitude of the audio signal.

B

In amplitude modulation the frequency of the high frequency carrier wave is made to vary in proportion to the amplitude of the audio signal.

C

In frequency modulation the amplitude of the high frequency carrier wave is made to vary in proportion to the amplitude of the audio signal.

D

In frequency modulation the amplitude of the high frequency carrier wave is made to vary in proportion to the frequency of the audio signal.

Question 79: Palette 79/82

JEE Mains 2015 MCQ

A signal of $5$ $kHz$ frequency is amplitude modulated on a carrier wave of frequency $2$ $MHz.$ The frequencies of the resultant signal is/are :

A

$2005$ $kHz, 2000$ $kHz$ and $1995$ $kHz$

B

$2000$ $kHz$ and $1995$ $kHz$

C

$2$ $MHz$ only

D

$2005$ $kHz$ and $1995$ $kHz$

Question 80: Palette 80/82

JEE Mains 2012 MCQ

A radar has a power of $1kW$ and is operating at a frequency of $10$ $GHz.$ It is located on a mountain top of height $500$ $m.$ The maximum distance upto which it can detect object located on the surface of the earth (Radius of earth $ = 6.4 \times {10^6}m$) is :

A

$80$ $km$

B

$16$ $km$

C

$40$ $km$

D

$64$ $km$

Question 81: Palette 81/82

JEE Mains 2011 MCQ

This 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 general, less stable then ground wave signals.
Statement -$2$ : The state of ionosphere varies from hour to hour, day to day and season to season.

A

Statement - $1$ is true, Statement - $2$ is true, Statement - $2$ is the correct explanation of Statement - $1$.

B

Statement - $1$ is true, Statement - $2$ is true, Statement - $2$ is not the correct explanation of Statement - $1$.

C

Statement - $1$ is false, Statement - $2$ is true

D

Statement - $1$ is true, Statement - $2$ is false.

Question 82: Palette 82/82

JEE Mains 2003 MCQ

Consider telecommunication through optical fibres. Which of the following statements is not true?

A

Optical fibres can be of graded refractive index

B

Optical fibres are subject to electromagnetic interference from outside

C

Optical fibres have extremely low transmission loss

D

Optical fibres may have homogeneous core with a suitable cladding.