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Electromagnetic Waves question

2021 · 27 Aug · Shift 2 · Q66
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Electromagnetic Waves question

2021 · 27 Aug · Shift 2 · Q66

JEE MainPhysicsElectromagnetic WavesNumerical+4 / −1
A plane electromagnetic wave with frequency of 30 MHz travels in free space. At particular point in space and time, electric field is 6 V/m. The magnetic field at this point will be x ×\times× 10 −-− 8 T. The value of x is ‾\underline{\hspace{2cm}}​.
Numerical answer
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Correct answer: 2

  1. For a plane electromagnetic wave in free space, the electric and magnetic fields are related by E=cBE = cBE=cB where c=3×108 m/sc = 3 \times 10^8\ \text{m/s}c=3×108 m/s.

  2. Given: E=6 V/mE = 6\ \text{V/m}E=6 V/m So, B=Ec=63×108B = \frac{E}{c} = \frac{6}{3 \times 10^8}B=cE​=3×1086​

  3. Calculate: B=2×10−8 TB = 2 \times 10^{-8}\ \text{T}B=2×10−8 T

  4. Comparing with the given form: B=x×10−8 TB = x \times 10^{-8}\ \text{T}B=x×10−8 T we get x=2x = 2x=2

Therefore, the required integer is 2.

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