{"id":539526,"date":"2021-09-22T09:26:11","date_gmt":"2021-09-22T09:26:11","guid":{"rendered":"https:\/\/www.indcareer.com\/schools\/?p=539526"},"modified":"2023-09-21T08:39:06","modified_gmt":"2023-09-21T08:39:06","slug":"ncert-solutions-for-12th-class-physics-chapter-15-communication-systems","status":"publish","type":"post","link":"https:\/\/www.indcareer.com\/schools\/ncert-solutions-for-12th-class-physics-chapter-15-communication-systems\/","title":{"rendered":"NCERT Solutions for 12th Class Physics: Chapter 15-Communication Systems"},"content":{"rendered":"\n

Class 12: Physics Chapter 15 solutions. Complete Class 12 Physics Chapter 15 Notes.<\/p>\n\n\n\n

NCERT Solutions for 12th Class Physics: Chapter 15-Communication Systems<\/h2>\n\n\n\n

NCERT 12th Physics Chapter 15, Class 12 Physics Chapter 15 solutions<\/p>\n\n\n\n

Question 1.<\/strong>
Which of the following frequencies will be suit-able for beyond-the-horizon communication using sky waves?
(a)<\/strong> 10 kHz
(b)<\/strong> 10 MHz
(c)<\/strong> 1 GHz
(d)<\/strong> 1000 GHz
Solution:<\/strong>
(b) :<\/strong> 10 MHz will be suitable frequency for sky waves as lower frequency of 10 kHz will require large radiating antenna and higher frequencies 1 GHz and 1000 GHz will pass through the ionosphere and will not be reflected by it.<\/p>\n\n\n\n

Question 2.<\/strong>
Frequencies in the UHF range normally propagate by means of:
(a)<\/strong> Ground waves
(b)<\/strong> Sky waves
(c)<\/strong> Surface waves
(d)<\/strong> Space waves
Solution:<\/strong>
(d) :<\/strong> Frequencies in the UHF range normally propagates by means of space waves. The high frequency space waves are ideal for frequency modulation but do not bend with ground.<\/p>\n\n\n\n

Question 3.<\/strong>
Digital signals<\/strong>
(i)<\/strong> do not provide a continuous set of values,
(ii)<\/strong> represent values as discrete steps,
(iii)<\/strong> can utilize binary system, and
(iv)<\/strong> can utilize decimal as well as binary systems.

Which of the above statements are true?<\/strong>
(a) (i)<\/strong> and (ii)<\/strong> only
(b) (ii)<\/strong> and (iii)<\/strong> only
(c) (i), (ii)<\/strong> and (iii)<\/strong> but not (iv)<\/strong>
(d)<\/strong> All of (i), (ii), (iii)<\/strong> and (iv)<\/strong>.
Solution:<\/strong>
(c) :<\/strong> Decimal system represents a continuous set of values which cannot be utilized by digital signals.<\/p>\n\n\n\n

Question 4.<\/strong>
Is it necessary for a transmitting antenna to be at the same height as that of the receiving antenna for the line of sight communication? A TV transmitting antenna is 81 m tall. How much service area can it cover if the receiving antenna is at the ground level?
Solution:<\/strong>
No, for line of sight communication, the two antenna may not be at the same height. Surface area
<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n
\"\"<\/figure>\n\n\n\n

Question 5.<\/strong>
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:<\/strong>
Modulation index, <\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

 so, peak voltage
\"{<\/p>\n\n\n\n

Question 6.<\/strong>
A modulating signal is a square wave, as shown in Figure
<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n


The carrier wave is given by c(t) = 2sin (8\u03c0t) volts
(i)<\/strong> Sketch the amplitude modulated wave form
(ii)<\/strong> What is the modulation index?
Solution:<\/strong>
(i)<\/strong> The amplitude modulated wave is shown here\u2019:
<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n


(ii)<\/strong> Modulation index, <\/p>\n\n\n\n

<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

Question 7.<\/strong>
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, p. What would be the value of p if the minimum amplitude is zero volt?
Solution:<\/strong>
We know
Modulation index, <\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n


Also, minimum amplitude, <\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n


Maximum amplitude, <\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n


So, modulation index, <\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n


or <\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n


if Amin<\/sub> = O, then modulation index, <\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

Question 8.<\/strong>
Due to economic reasons, only the upper side band 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:<\/strong>
Let, the received signal be cos(\u03c9c<\/sub> + \u03c9m<\/sub>)t The carrier signal available at the receiving station is Ac<\/sub> cos \u03c9c<\/sub>t Multiplying the two signals, we get A1<\/sub>Ac<\/sub> cos  (\u03c9c<\/sub> + \u03c9m<\/sub>)t cos \u03c9c<\/sub>t <\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

 If this signal is passed through a low pass filter, we can recover the modulating signal <\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

NCERT Solutions for 12th Class Physics: Chapter 1: Download PDF<\/strong><\/h2>\n\n\n\n

NCERT Solutions for 12th Class Physics: Chapter 1-Electric Charges And Fields<\/p>\n\n\n\n

Download PDF<\/strong>: NCERT Solutions for 12th Class Physics: Chapter 1-Electric Charges And Fields PDF<\/a><\/p>\n\n\n\n

Chapterwise NCERT Solutions for Class 12 Physics <\/strong>:<\/h2>\n\n\n\n