class 12 communication system short question answer

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हिन्दी में पढ़ें  

Q.1.  – What is Ionosphere?

Ans. – The part of atmosphere,which is extended from 80 km to 400 km is called ionosphere.

                                  It plays main role in sky – wave communications because it reflects some frequencies of radio waves.

Q.2.  – Why satellites are used in long distance T.V. transmission?                                                                                

Ans. – Frequency of T.V. signal is high. Which is not reflected by ionosphere this is why – satellites are used in long distance T.V. transmission.

Q.3. – What is meaning of “modulation index is 75%”?

Ans. – since we know that

            Amplitude modulation index = Am/Ac

          or, 75% = Am/Ac

         or,75/100 =Am/Ac

         or,  Am/Ac = ¾

             Am/Ac = 3:4

Hence ratio  of (message wave)Am to (carrier wave) Ac  is 3:4 

chapter 1 ELECTRIC CHARGES AND FIELDS short Q-A
chapter 2 ELECTROSTATIC POTENTIAL AND CAPACITANCE short Q-A
chapter 3 CURRENT ELECTRICITY short Q-A
chapter 4 MOVING CHARGES AND MAGNETISM short Q-A
chapter 5 MAGNETISM AND MATTER short Q-A
chapter 6 ELECTROMAGNETIC INDUCTION short Q-A
chapter 7 ALTERNATING CURRENT short Q-A
chapter 8  ELECTROMAGNETIC WAVES short Q-A

chapter 9 RAY OPTICS AND OPTICAL INSTRUMENTS short Q-A
chapter 10 WAVE OPTICS short Q-A
chapter 11 DUAL NATURE OF RADIATION AND MATTER short Q-A 

chapter 12 ATOMS short Q-A

chapter 13 NUCLEI short Q-A 

chapter 14 SEMICONDUCTORS ELECTRONICS short Q-A