12th Standard CBSE Syllabus & Materials
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Published on: 27/05/2021
CBSE 12th Standard Physics Subject Communication Systems HOT Questions 1 Mark Questions 2021
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Questions + Answers key
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1.
Why are micro wave used in radars?
2.
The carrier wave is given by C(t) = 2 sin \((8\pi t)\) volt. The modulating signal is a square wave as shown. Find modulation index.
3.
In the given diagram C(t) stands for the carrier wave and m(t) for the signal to be transmitted. What name do we give to the wave labelled as Cm(t) in the diagram?
4.
Why are microwave considered better carriers of signals than ratio waves?
5.
How are side bands produced?
1.
( )
In a radar, a beam signal is needed in particular direction which is possible if wavelength of signal waves is very small. Since the wavelength of microwave is a few millimeter, hence they are used in radar.
2.
( )
\(Modulation\ Index\ =\ \frac { { a }_{ 2 } }{ { a }_{ 1 } }\)
\(=1/2=0.5\)
3.
( )
Cm(t) is the frequency modulated wave.
4.
( )
On account of smaller wavelength of microwaves, they can be transmitted as beam signals in a particular direction, much better than radio waves, as microwaves do not bend around the corners of the obstacles coming in their way.
5.
( )
Side bands are produced during the process of modulation.During modulation, the audio frequency modulating signal wave is superimposed on a high-frequency wave, called carrier wave.Any form of modulation produces frequencies that are the sum and the differences of the carrier and modulating frequencies.
These frequencies are called sidebands
Lower sideband frequency = fc - fm
Upper sideband frequency = fc + fm
12th Standard CBSE Syllabus & Materials
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