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Nature of EM Waves & Wave Equation question from NEET 2018

Q70NEET 2018Easy

Nature of EM Waves & Wave Equation

An EM wave is propagating in a medium with a velocityv⃗=vi^\vec{v} = v\hat{i}. The instantaneous oscillating electric field of this em wave is along +y axis. Then the direction of oscillating magnetic field of the em wave will be along

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Answer: (b)

v (+x)E (+y)B (+z)
  1. Direction of propagation is E⃗×B⃗\vec{E}\times\vec{B}.
  2. i^=j^×B^\hat{i} = \hat{j}\times\hat{B} needs B^=k^\hat{B} = \hat{k}, since j^×k^=i^\hat{j}\times\hat{k} = \hat{i}.
  3. So the answer is (b) +z direction.
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