Ch 10Communication Systems — Class 12 Physics, concept-first.

Communication -- the exchange of information from one point to another -- has existed since the dawn of human life, but the growth of science and technology over the last two centuries removed the "lo…

Over short distances, an information (baseband) signal carries enough energy on its own to be sent directly with no special processing -- a person's voice reaches a nearby listener without any electro…

Amplitude modulation (AM) is the scheme in which the amplitude of the carrier signal is varied in direct proportion to the instantaneous amplitude of the baseband signal, while the carrier's frequency…

Frequency modulation (FM) is the scheme in which the frequency of the carrier signal is varied in proportion to the instantaneous amplitude of the baseband signal, while the carrier's own amplitude an…

Phase modulation (PM) is the scheme in which the instantaneous amplitude of the baseband signal modifies only the phase of the carrier signal, while the carrier's amplitude and frequency are both held…

Electronic communication is, at its core, the transmission of sound, text, pictures or data through a medium -- typically free space for long-distance links -- and every practical communication system…

Bandwidth, in the context of a single information (baseband) signal, is the frequency range that signal actually occupies -- for instance the range spanned by voice, music or picture data.

Bandwidth of transmission system (or channel bandwidth) is the range of frequencies a particular communication channel must be allotted in order to carry a specified piece of information -- in other w…

An antenna, present at both the transmitting and the receiving end of a wireless link, must have a height that is a specific fraction of the wavelength of the signal it is meant to carry -- specifical…

Once a baseband signal has been modulated onto a carrier wave and radiated by the transmitting antenna, it must actually travel across the intervening space to reach the receiving antenna at the other…

Ground wave (or surface wave) propagation is the mode in which electromagnetic waves radiated by the transmitter glide directly along the surface of the Earth to reach the receiver, rather than travel…

Sky wave (or ionospheric) propagation is the mode in which electromagnetic waves radiated from an antenna directed steeply upward, at large angles to the ground, are reflected by the ionosphere back d…

Space wave propagation is the mode used for sending and receiving an information signal directly through space at very high frequencies, above roughly 30 MHz -- these are called space waves, and becau…

Satellite communication is the mode of communicating a signal between a transmitter and a receiver by relaying it through an artificial satellite.

Fibre-optic communication is the method of transmitting information from one place to another as pulses of light travelling through an optical fibre, working on the underlying principle of total inter…

RADAR stands for RAdio Detection And Ranging -- one of the most important applications of communication systems, used to sense, detect and precisely locate distant objects such as aircraft, ships and…

Mobile communication lets people communicate with one another across different locations without needing any physical connection such as wires or cables, allowing transmission over a wide area and let…

The Internet is a fast-growing communication technology offering a multifaceted set of tools, providing new ways for people to interact and connect with one another -- it is, in fact, the largest comp…

GPS stands for Global Positioning System -- a global navigation satellite system that provides geolocation (a precise position) and accurate time information to a GPS receiver anywhere on or near the…

Information and communication technology (ICT) has moved well beyond conventional telecom into sectors such as agriculture, fisheries and mining, where it enhances productivity, improves the living st…

This unit's core results, gathered in one place: the basic elements needed to transmit and receive a signal over a long distance using electromagnetic waves are a transducer, an amplifier, a carrier s…

The chapter's own concept map is rooted at "Communication system" and branches out along the transmission chain: an input (information) signal is picked up by a transducer, boosted by an amplifier, co…

The unit closes with the textbook's own list of further-reading references for students who want to study communication systems in more depth than the school syllabus covers: (1) B.L.

The unit's ICT Corner activity, titled "Communication systems" with the topic Amplitude Modulation, is a short hands-on demonstration meant to make the abstract idea of AM concrete and visual.

The unit closes with a three-part end-of-chapter Evaluation. Part I is five Multiple Choice Questions, each with four options and the book's own printed answer key, covering the output transducer, whe…

Sample papers and previous-year board questions for this subject.