CBSE 12th Standard Physics Subject Communication Systems Value Based Questions 3 Mark Questions With Solution 2021
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CBSE 12th Standard Physics Subject Communication Systems Value Based Questions 3 Mark Questions With Solution 2021
12th Standard CBSE
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Reg.No. :
Physics
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Arun lives in Delhi, His grandfather lives in a small village in Haryana.He always misses his grandfather, so he decided to purchase a mobile phone for his grandfather.He saved his pocket money and purchased the mobile phone.Now his grandfather communicates often with his family and now they are happy.
(a) What are the values Arun displayed in his act?
(b) Name the type of wave used in mobile communication.Write its frequency range.(a) -
Rita was studying in 10th class, one day she asked her father to explain the working of remote control of TV. Her father was not knowing the answer, but he made up his mind to understand the working of remote control. He found one shop where remote controls were repaired. The shopkeeper showed to Rita's father the inside of the remote control and explained her the working. Rita's father explained her the working of remote control, Rita was happy and satisfied.
(a) What are the values Rita's father displayed in his act?
(b) Name the diode used in remote control.(a) -
Modulation is the phenomenon of superimposing the low audio frequency base band message or information signals (called the modulating signals) on a high frequency wave (called, the carrier wave). The resultant wave is called the modulated wave, which is transmitted.
Read the above passage and answer the following questions:
(i) What are the Audio frequency and Radio Frequency ranges?
(ii) Why audio frequency signals, as such cannot be transmitted over long distances?
(iii) What does the phenomenon imply in day to day life?(a) -
Demodulation is the reverse process of modulation, which is performed in a receiver to recover the original modulating signals. At the receiving end, the signals are generally weak due to attenuation in the channel. The receiver selects only the desired signal, rejecting the unwanted (noise) signals and amplifies the same.
Read the above passage and answer the following questions:
(i) What are the main functions of a demodulator?
(ii) Give any two examples of demodulators.
(iii) What does the phenomenon of demodulation imply in day to day life?(a)
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CBSE 12th Standard Physics Subject Communication Systems Value Based Questions 3 Mark Questions With Solution 2021 Answer Keys
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(a) Values displayed by Arun are Affection, attitude, Respect to elders, Caring, Responsible and helpfulness.
(b) The waves used in mobile communication are microwaves having range 450 MHz to 2100 MHz. -
(a) Rita's father takes interest to understand the working of the mind of his daughter and make effort to satisfy her desire for knowledge.
(b) The diode used are LED(Light Emitting Diode). -
(i) The AF range is 20 Hz to 20 kHz and RF range is 5 x 105 Hz to 109 Hz.
(ii) Audio frequency signals, as such cannot be transmitted over long distances because size of antenna required is too large; effective power radiated is small and mixing up of signals from different transmitters causes problems.
(iii) In day to day life, modulation is so evident. For example, we cannot travel long distances on foot. We have to travel by air or by train or car/bus. They act as our carriers, carrying us to our destinations at long distances. -
(i) The main functions of a demodulator are:
(a) selecting the desired signal and rejecting the unwanted signals.
(b) demodulating the desired signal and amplifying it.
(c) displaying the original modulating signal in a desired manner.
(ii) All receivers like television and radio are demodulators.
(iii) In day to day life, demodulation is so common. An aeroplane, for example carries us to our destination town. we get off the plane and meet our loved ones. The carrier is to be left behind. In a demodulator, carrier wave is bypassed and only the original modulating signal is reproduced.
