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JEE Main 2019 (12 Jan, Shift 2) · Energy Density & Intensity

Energy Density & Intensity question from JEE Main 2019 (12 Jan, Shift 2)

Q29JEE Main 2019 · 12 JAN · SHIFT 2Medium

Energy Density & Intensity

The mean intensity of radiation on the surface of the Sun is about 108 W/m2. The rms value of the corresponding magnetic field is closet to:

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Answer: (c)

  1. I=cBrms2μ0⇒Brms=μ0IcI = \dfrac{c B_{rms}^2}{\mu_0} \Rightarrow B_{rms} = \sqrt{\dfrac{\mu_0 I}{c}}
  2. Brms=4π×10−7×1083×108=4.2×10−7≈6.5×10−4B_{rms} = \sqrt{\dfrac{4\pi \times 10^{-7} \times 10^{8}}{3 \times 10^{8}}} = \sqrt{4.2 \times 10^{-7}} \approx 6.5 \times 10^{-4} T
  3. Closest order of magnitude is 10−410^{-4} T.
  4. So the answer is (c) 10−410^{-4} T.
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