Electromagnetic Waves

JEE Main level, single correct, medium

65 of 165

Question 65 of 165

Given below are two statements :
Statement I: A time varying electric field is a source of changing magnetic field and vice-versa. Thus a disturbance in electric or magnetic field creates EM waves.
Statement II: In a material medium, the EM wave travels with speed v=1μ0ϵ0v=\dfrac{1}{\sqrt{{\mu }_{0}{ϵ}_{0}}}.
In the light of the above statements, choose the correct answer from the options given below.

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Answer: (C) Statement I is correct but statement II is false

According to the Maxwell’s EM theory, the EM waves propagation contains electric and magnetic field vibration in mutually perpendicular direction. Thus, the changing of electric field give rise to magnetic field.
Also, time varying magnetic field produces electric field. According to Faradays law, when magnetic flux changes in the region surrounded by conductor, it produces electric field (induced emf) in conductor.
In a material medium the EM wave travels with speed given by v=1μϵv=1μ0μr(ϵ0ϵr)\begin{matrix}v & =\dfrac{1}{\sqrt{\mu \epsilon }} \\ v & =\dfrac{1}{\sqrt{{\mu }_{0}{\mu }_{r}({\epsilon }_{0}{\epsilon }_{r})}}\end{matrix}
Thus, statement I is correct but statement II is false.

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