NCERT Solutions For Class 12 Physics Chapter 15 Communications System
NCERT Solutions For Class 12 Physics Chapter 15: Get NCERT Solutions for Class 12 Physics chapter 15-Communication Systems prepared by academic team of Physics Wallah
Krati Saraswat9 Feb, 2024
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NCERT Solutions For Class 12 Physics Chapter 15 Communications System
NCERT Solutions For Class 12 Physics Chapter 15 Communications System is prepared by our senior and renowned teachers of Physics Wallah primary focus while solving these questions of class-12 in NCERT textbook, also do read theory of this Chapter 15 Communications System while going before solving the NCERT questions. You can download and share NCERT Solutions of Class 12 Physics from Physics Wallah.NCERT Solutions For Class 12 Physics Chapter 15 Overview
With the help of NCERT Solutions for class 12 physics chapter 15 solutions, students can practise more efficiently and gradually grasp ideas, which improves test scores. The professors at Physics Wallah developed these solutions with the goal of increasing comprehension. By going over and practicing these answers, the intention is to assist students in achieving high test scores.NCERT Solutions For Class 12 Physics Chapter 15 PDF
Expert teachers have developed NCERT Solutions For Class 12 Physics Chapter 15. It covers every concept covered in the chapter and has a lot of practice problems with detailed explanations. With the help of these solutions, students can practise more efficiently and gradually grasp ideas, which improves test scores. Physics Wallah's experienced instructors have carefully produced these NCERT Solutions Class 12 Physics Chapter 15 to help students better understand the concepts discussed in this chapter. The intention is to make getting good grades on tests easier by using and practicing with these solutions.NCERT Solutions Class 12 Physics Chapter 15 PDF Download Link
NCERT Solutions For Class 12 Physics Chapter 15
Answer The Following Question Answer NCERT Solutions For Class 12 Physics Chapter 15 Communications System:
Question 1. Which of the following frequencies will be suitable for beyond-the-horizon communication using sky waves? (a) 10 kHz (b) 10 MHz (c) 1 GHz (d) 1000 GHz Solution : (b) 10 MHz For beyond-the-horizon communication, it is necessary for the signal waves to travel a large distance. 10 KHz signals cannot be radiated efficiently because of the antenna size. The high energy signal waves (1GHz − 1000 GHz) penetrate the ionosphere. 10 MHz frequencies get reflected easily from the ionosphere. Hence, signal waves of such frequencies are suitable for beyond-the-horizon communication. Question 2. Frequencies in the UHF range normally propagate by means of: (a) Ground waves. (b) Sky waves. (c) Surface waves. (d) Space waves. Solution : (d) Space waves Owing to its high frequency, an ultra high frequency (UHF) wave can neither travel along the trajectory of the ground nor can it get reflected by the ionosphere. The signals having UHF are propagated through line-of-sight communication, which is nothing but space wave propagation. Question 3. Digital signals (i) Do not provide a continuous set of values, (ii) Represent values as discrete steps, (iii) Can utilize binary system, and (iv) Can utilize decimal as well as binary systems. Which of the above statements are true? (a) (i) and (ii) only (b) (ii) and (iii) only (c) (i), (ii) and (iii) but not (iv) (d) All of (i), (ii), (iii) and (iv). Solution : (c) A digital signal uses the binary (0 and 1) system for transferring message signals. Such a system cannot utilise the decimal system (which corresponds to analogue signals). Digital signals represent discontinuous values. Question 4. Is it necessary for a transmitting antenna to be at the same height as that of the receiving antenna for line-of-sight communication? A TV transmitting antenna is 81m tall. How much service area can it cover if the receiving antenna is at the ground level? Solution : Line-of-sight communication means that there is no physical obstruction between the transmitter and the receiver. In such communications it is not necessary for the transmitting and receiving antennas to be at the same height. Height of the given antenna, h = 81 m Radius of earth, R = 6.4 × 106 m For range, d = (2Rh)½, the service area of the antenna is given by the relation: A = πd2 = π (2Rh) = 3.14 × 2 × 6.4 × 106 × 81 = 3255.55 × 106 m2 = 3255.55 ∼ 3256 km2 Question 5. A carrier wave of peak voltage 12 V is used to transmit a message signal. What should be the peak voltage of the modulating signal in order to have a modulation index of 75%? Solution : Amplitude of the carrier wave, Ac = 12 V Modulation index, m = 75% = 0.75 Amplitude of the modulating wave = Am Using the relation for modulation index:
Question
6. A modulating signal is a square wave, as shown in Fig. 15.14.
The carrier wave is given by:
(i) Sketch the amplitude modulated waveform
(ii) What is the modulation index?
Solution :
It can be observed from the given modulating signal that the amplitude of the modulating signal, Am = 1 V
It is given that the carrier wave c (t) = 2 sin (8πt)
∴Amplitude of the carrier wave, Ac = 2 V
Time period of the modulating signal Tm = 1 s
The angular frequency of the modulating signal is calculated as:
......(i)
The angular frequency of the carrier signal is calculated as:
.......(ii)
From equations (i) and (ii), we get:
The amplitude modulated waveform of the modulating signal is shown in the following figure.
(ii)Modulation index,
Question
7.For an amplitude modulated wave, the maximum amplitude is found to be 10 V while the minimum amplitude is found to be 2 V. Determine the modulation index μ. What would be the value of μ if the minimum amplitude is zero volt?
Solution :
Maximum amplitude, Amax = 10 V
Minimum amplitude, Amin = 2 V
Modulation index μ, is given by the relation:
.png)
Question
8. Due to economic reasons, only the upper sideband of an AM wave is transmitted, but at the receiving station, there is a facility for generating the carrier. Show that if a device is available which can multiply two signals, then it is possible to recover the modulating signal at the receiver station.
Solution :
Let ωc and ωs be the respective frequencies of the carrier and signal waves.
Signal received at the receiving station, V = V1 cos (ωc + ωs)t
Instantaneous voltage of the carrier wave, Vin = Vc cos ωct
At the receiving station, the low-pass filter allows only high frequency signals to pass through it. It obstructs the low frequency signal ωs. Thus, at the receiving station, one can record the modulating signal
, which is the signal frequency.
NCERT Solutions For Class 12 Physics Chapter 15 FAQs
What are the elements of communication system class 12 physics?
No matter its nature, each communication system has 3 essential elements: transmitter, medium/channel, and receiver.
What is a main element of a communication system?
The major elements of communication are the Transmitter of information, the Channel or medium of communication and the Receiver of information.
How many elements are essential for any communication system?
Communication is the very act of transmission of information. Irrespective of its nature, every communication system has three essential elements, namely a transmitter, a medium or channel, and a receiver.
Why modulation is used in communication system?
The primary purpose of modulation in a communication system is to generate a modulated signal suited to the characteristics of a transmission channel.
What are the uses of communication system?
The purpose of a communication system is to transmit an intelligence signal from a source to a destination at some point away from the source.
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