Em Waves Question 91
Question: The rms value of the electric field of the light coming from the Sun is $ 720N/C $ . The average total energy density of the electromagnetic wave is
Options:
A) $ 4.58\times {{10}^{-6}}J/m^{3} $
B) $ 6.37\times {{10}^{-9}}J/m^{3} $
C) $ 81.35\times {{10}^{-12}}J/m^{3} $
D) $ 3.3\times {{10}^{-3}}J/m^{3} $
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Answer:
Correct Answer: A
Solution:
[a] $ E _{rms}=720 $ The average total energy density $ =\frac{1}{2}{\in _{0}}E _{0}^{2}=\frac{1}{2}{\in _{0}}{{[\sqrt{2}E _{rms}]}^{2}}={\in _{0}}E _{rms}^{2} $
$ =8.85\times {{10}^{-12}}\times {{(720)}^{2}}=4.58\times {{10}^{-6}},J/m^{3} $
BETA
