XII Physics, Chapter 8 & 15 Electro magnetic waves and communication Chapter8 & 15 electromagnetic waves & communicatio | Page 4

U E = 1 / 2 ε o E 2 = 1 / 4 ε o E 2 o
( viii ) The average magnetic energy
density , U B = 1 / 2 B 2 / μ o = 1 / B 2 o / μ o
( ix ) The electric vector is responsible for the optical effects of an electromagnetic wave .
( x ) Intensity of electromagnetic wave is defined as energy crossing per unit area per unit time perpendicular to the directions of propagation of electromagnetic wave .
( xi ) The intensity I is given by the relation , I = < μ > c = 1 / 2 ε o E 2 oc
( xii ) The existence of electromagnetic waves was confirmed by Hertz experimentally in 1888 .
Propagation of Electromagnetic Waves
In radio wave communication between two places . the electromagnetic waves are radiated out by the transmitter antenna at one place which travel through the space and reach the receiving antenna at the other place .
Electromagnetic Spectrum