Page 193 - Computer_Science_F5

Computer Science between the sender and receiver is done with the help of a satellite. The signal,
which is a beam of modulated microwaves, is sent toward the satellite. Then the
satellite amplifies the signal and sends it back to the receiver’s antenna present on
the earth’s surface. So, all the signal transferring is happening in space. Thus, this
type of communication is known as space communication. Some of the properties
FOR ONLINE READING ONLY
of each wave are listed in Table 3.9.

Table 3.9: Classification of transmission waves and their properties

Transmission waves Properties
Radio waves (i) Waves of frequency range from 3 kHz to 1GHz.

(ii) Radio waves are multi-directional, can move in all
directions.
(iii) Radio waves of frequency 300 kHz-30 MHz can travel
long distances.

(iv) They are susceptible to interference.
(v) Radio waves of frequencies from 3 kHz to 300 kHz
can penetrate walls.

(vi) These waves are used in AM and FM radio, television,
and cordless phones.

Microwaves (i) Electromagnetic waves of frequency range from 1 GHz
to 300 GHz; Unidirectional, it can move in only one
direction; They cannot penetrate solid objects such
as walls, hills, or mountains; They need line-of-sight
propagation; that is, both communicating antennae
must be in the direction of each other; They are used
in point-to-point or unicast communications such as
radar and satellite; Provide very large information-
carrying capacity.

Infrared waves (i) Electromagnetic waves of frequency range from 300
GHz to 400 THz; Very high-frequency waves; They
cannot penetrate solid objects such as walls, hills,
or mountains; Used for short-distance point-to-point
communication such as mobile-to-mobile, mobile-to-
printer, remote-control-to-TV, and Bluetooth-enabled
devices to other devices.

184
for Advanced Secondary Schools

Computer Science Form 5.indd 184 23/07/2024 12:33