NEET-XII-Physics
40: Electromagnetic Waves
- #8A laser beam has intensity 2.5 × 1014 W m-2. Find amplitudes of electric and magnetic fields in the beam.Ans : Given:
Intensity, I = 2.5 × 1014 W/m2
We know:
`` I=\frac{1}{2}{\in }_{0}{{E}_{0}}^{2}c``
`` \Rightarrow {{E}_{0}}^{2}=\frac{2I}{{\mathit{\in }}_{0}c}``
`` \Rightarrow {E}_{0}=\sqrt{\frac{2I}{{\mathit{\in }}_{0}c}}``
`` \Rightarrow {E}_{0}=\sqrt{\frac{2\times 2.5\times {10}^{14}}{8.85\times {10}^{-12}\times 3\times {10}^{8}}}``
`` \Rightarrow {E}_{0}=0.4339\times {10}^{9}``
`` \Rightarrow {E}_{0}=4.33\times {10}^{8}\,\mathrm{\,N\,}/\,\mathrm{\,C\,}``
Maximum value of magnetic field,
`` {B}_{0}=\frac{{E}_{0}}{c}``
`` {B}_{0}=\frac{4.33\times {10}^{8}}{3\times {10}^{8}}``
`` \Rightarrow {B}_{0}=1.43\,\mathrm{\,T\,}``
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