Class 12 Physics Electromagnetic Waves Energy of EM wave

Energy of EM wave

  • As the EM waves propagate they carry energy.
  • Because of this property they have so many practical uses in our day-to-day life.
  • Energy in EM wave is partly carried by electric field and partly by magnetic field.
  • Mathematically:
    • Total energy stored per unit volume in EM wave ET =Energy stored per unit volume by electric field + Energy stored per unit volume stored in magnetic field.
    • =(1/2)(E2ε0) + (1/2)(B2μ0)
    • Experimentally it has been found that the;
    • Speed of the EM wave =Speed of the light c=(E/B)
    • => B=(E/c)
    • ET =(1/2)(E2ε0) + (1/2)( E2/c2μ0)
    • From Maxwell’s equations :- c=(1/√μ0ε0)
    • Therefore ,ET =(1/2)(E2ε0) + (1/2)( E2μ0ε00)
    • =(1/2)(E2ε0) + (1/2)(E2ε0)
    • ET = E2ε0
    • This is the amount of energy carried per unit volume by the EM wave.

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