NEET-XII-Physics
40: Electromagnetic Waves
Qstn# iv-9 Prvs-Qstn
- #9The intensity of the sunlight reaching Earth is 1380 W m-2. Assume this light to be a plane, monochromatic wave. Find the amplitudes of electric and magnetic fields in this wave.Ans : Given:
`` I=1380\,\mathrm{\,W\,}/{\,\mathrm{\,m\,}}^{2}``
`` I=\frac{1}{2}{\in }_{0}{{E}_{0}}^{2}c``
`` \Rightarrow {E}_{0}=\sqrt{\frac{2I}{{\in }_{0}c}}``
`` \Rightarrow {E}_{0}=\sqrt{\frac{2\times 1380}{8.83\times {10}^{-12}\times 3\times {10}^{8}}}``
`` \Rightarrow {E}_{0}=103.95\times {10}^{4}``
`` \Rightarrow {E}_{0}=10.195\times {10}^{2}``
`` \Rightarrow {E}_{0}=1.02\times {10}^{3}\,\mathrm{\,N\,}/\,\mathrm{\,C\,}``
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`` \,\mathrm{\,Since\,}{E}_{0}={B}_{\mathit{0}}c,``
`` {B}_{0}=\frac{{E}_{0}}{c}=\frac{1.02\times {10}^{2}}{3\times {10}^{28}}``
`` \Rightarrow {B}_{0}=3.398\times {10}^{-6}``
`` \Rightarrow {B}_{0}=3.4\times {10}^{-6}\,\mathrm{\,T\,}``