Please Explain about Electromagnetic waves of class 12
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Answer:
Electromagnetic Waves
Electromagnetic waves are those waves in which electric and magnetic field vectors changes sinusoidally and are perpendicular to each other as well as at right angles to the direction of propagation of wave.
The equation of plane progressive electromagnetic wave can be written as E = Eo sin Ω (t – x / c) and B = Bo sin Ω (t – x / c). Where, Ω =2πv
Electromagnetic waves are produced by accelerated charge particles.
Properties of EM Waves
(i) These waves are transverse in nature.
(ii) These waves propagate through space with speed of light, i.e., 3 * 108 m / s.
(iii) The speed of electromagnetic wave,
c = 1 / √μo εo
where, μoo is permittivity of free space,
∴ c = Eo / Bo
where Eo and Bo are maximum values of electric and magnetic field vectors.
[According to Maxwell, when a charged particle is accelerated, it produces electromagnetic wave. The total radiant flux at any instant is given by,
p = q2a2 / 6 πεoc2
(iv) The rate of flow of energy in an electromagnetic wave is described by the vector S called the poynting vector, which is ; defined by the expression,
S = 1 / μo E * B
SI unit of Sis watt/m2.
(v) Its magnitude S is related to the rate at which energy is transported by a wave across a unit area at any instant.
(vi) The energy in electromagnetic waves is divided equally between electric field and magnetic field vectors.
(vii) The average electric energy density.
UE = 1 / 2 εo E2 = 1 / 4 εo E2o
(viii) The average magnetic energy density,
UB = 1 / 2 B2 / μo = 1 / B2o / μo
(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 εo E2oc
(xii) The existence of electromagnetic waves was confirmed by Hertz experimentally in 1888.
Answer:
Electromagnetic waves are those waves in which electric and magnetic field vectors changes sinusoidally and are perpendicular to each other as well as at right angles to the direction of propagation of wave. Electromagnetic waves are produced by accelerated charge particles.