A) \[3.3\times {{10}^{-3}}J/{{m}^{3}}\]
B) \[4.58\times {{10}^{-6}}J/{{m}^{3}}\]
C) \[6.37\times {{10}^{-9}}J/{{m}^{3}}\]
D) \[81.35\times {{10}^{-12}}J/{{m}^{3}}\]
Correct Answer: B
Solution :
[b] In electromagnetic waves, electric energy density is equal to magnetic energy density. Total energy density \[=2\times \text{electric}\,\,\text{energy}\] \[=2\left( \frac{1}{2}{{\varepsilon }_{0}}{{E}^{2}} \right)\] \[=2\times 12\times 8.854\times {{10}^{-12}}\times {{(720)}^{2}}\] \[=4.58\times {{10}^{-6}}J\text{/}{{m}^{3}}\]
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