Q.Write the frequency allocation table for the different communication systems.

To send a message through free space, information is first turned into electromagnetic (radio-frequency) waves — sinusoidal oscillations in which a time-varying electric field and magnetic field lie perpendicular to each other and to the direction of travel. These waves radiate outward and travel at the speed of light, $3\times10^{8}$ m/s, making them ideal carriers for both short- and long-distance communication.

The radio portion of the electromagnetic spectrum spreads over an enormous range of frequencies, from about $10^{4}$ Hz to $10^{14}$ Hz. Rather than treat this as one continuous block, it is divided into named frequency bands, each with its own propagation behaviour and typical uses:

The key idea is that frequency decides behaviour: low frequencies hug the earth, high frequencies bounce off the ionosphere, and very high frequencies travel in straight lines. This is why the spectrum is allocated band by band to the services each suits best — a recurring theme in the Karnataka 2nd PUC Electronics course.