Communication System JEE Main previous year questions with solutions

5 solved JEE Main questions on Communication System, free to read — no sign-in needed. The full chapter has 109 questions; sign in to attempt the remaining 104 in the exam simulator.

Answers checked against the official answer keys.

1. Q1JEE Main 2023 (15 Apr, Shift 1)
   The height of transmitting antenna is $180m$ and the height of the receiving antenna is $245m$. The maximum distance between them for satisfactory communication in line of sight will be: (given $R=6400km$)
   1. A.$96km$
   2. B.$56km$
   3. C.$48km$
   4. D.$104km$
   Show answer & solution

   Answer: (D)

   The maximum distance for line of sight communication is $d=\sqrt{2hR}+\sqrt{2h'R}$ The given data is $R=6400km h=180m$ $h'=245m$ Thus, the value is $d=\sqrt{2\times 180\times 6400\times {10}^{3}}$ $+\sqrt{2\times 245\times 6400\times {10}^{3}}$ $=6\times 80\times {10}^{2}+7\times 80\times {10}^{2}$ $=104km$
2. Q2JEE Main 2021 (16 Mar, Shift 1)Basics of Mechanical Waves
   A $25m$ long antenna is mounted on an antenna tower. The height of the antenna tower is $75m$. The wavelength (in meter) of the signal transmitted by this antenna would be :
   1. A.$300$
   2. B.$400$
   3. C.$200$
   4. D.$100$
   Show answer & solution

   Answer: (D)

   Length of Antena $=25m=\dfrac{\lambda }{4}$ $\Rightarrow \lambda =100m$
3. Q3JEE Main 2019 (10 Apr, Shift 1)Electromagnetic Spectrum
   Given below in the left column are different modes of communication using the kinds of waves given in the right column. (1) Optical Fibre Communication (P) Ultrasound (2) Radar (Q) Infrared Light (3) Sonar (R) Microwaves (4) Mobile Phones (S) Radio Waves From the options given below, find the most appropriate match between entries in the left and the right column.
   1. A.$1-Q,2-S,3-P,4-R$
   2. B.$1-S,2-Q,3-R,4-P$
   3. C.$1-Q,2-S,3-R,4-P$
   4. D.$1-R,2-P,3-S,4-Q$
   Show answer & solution

   Answer: (A)

   Optical fibre – Infrared light RADAR – Radiowaves SONAR – Ultrasound Mobile Phones – Microwaves
4. Q4JEE Main 2023 (13 Apr, Shift 2)
   To radiate EM signal of wavelength $\lambda$ with high efficiency, the antennas should have a minimum size equal to:
   1. A.$2\lambda$
   2. B.$\dfrac{\lambda }{2}$
   3. C.$\dfrac{\lambda }{4}$
   4. D.$\lambda$
   Show answer & solution

   Answer: (C)

   For efficient radiation and reception, the height of transmitting and receiving antennas should be comparable to a quarter of wavelength of the frequency used. So for efficient transmission of signals of wavelengths$\lambda$ the minimum length of antenna should be $\dfrac{\lambda }{4}$.
5. Q5JEE Main 2023 (13 Apr, Shift 1)
   Match List-I with List-II List-I (Layer of atmosphere) List-II (Approximate height over earth's surface) $(A)$ ${F}_{1}-$Layer $(I)$ $10km$ $\left(B\right)$ $D-$Layer $\left(II\right)$ $170-190km$ $\left(C\right)$ Troposphere $\left(III\right)$ $100km$ $\left(D\right)$ $E-$Layer $\left(V\right)$ $65-75km$ Choose the correct answer from the options given below.
   1. A.$A–II,B–IV,C–I,D–III$
   2. B.$A–II,B–IV,C–III,D–I$
   3. C.$A–III,B–IV,C–I,D–II$
   4. D.$A–II,B–I,C–IV,D–III$
   Show answer & solution

   Answer: (A)

   The ${F}_{1}$ layer is above the E layer and the ionization is less compared to E layer. It ranges to $170-190km$. The D layer is located above the stratosphere. It ranges from $60-90km$ above the earth's surface. The troposphere starts from the ground and ranges to $100km$. The E layer is located above the D layer. The intensity of ionization is less than the D layer. It ranges from $100-125km$ above the earth's surface.