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JEE Main 2020 (8 Jan, Shift 2) · Nature of EM Waves & Wave Equation

Nature of EM Waves & Wave Equation question from JEE Main 2020 (8 Jan, Shift 2)

Q55JEE Main 2020 · 8 JAN · SHIFT 2Medium

Nature of EM Waves & Wave Equation

A plane electromagnetic wave of frequency 25 GHz is propagating in vacuum along the z-direction. At a particular point in space and time, the magnetic field is given by B⃗=5×10−8j^ T\vec{B} = 5\times 10^{-8}\hat{j}\text{ T}. The corresponding electric field E⃗\vec{E} is (speed of light c = 3 × 108 ms–1)

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Answer: (a)

  1. E=cB=3×108×5×10−8=15E = cB = 3\times10^{8}\times5\times10^{-8} = 15 V/m (frequency not needed).
  2. Need E^×j^=k^\hat E\times\hat j = \hat k: i^×j^=k^\hat i\times\hat j = \hat k, so E⃗\vec E along +i^+\hat i.
  3. So the answer is (a) 15 i^15\,\hat i V/m.
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