Em Waves Question 76
Question: The rms value of the electric field of the light coming from sun is 720 N/C. The average energy density of the emf is
Options:
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} $
Show Answer
Answer:
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( \frac{1}{2}{\varepsilon _{0}}E^{2} ) $
$ =2\times 12\times 8.854\times {{10}^{-12}}\times {{(720)}^{2}} $
$ =4.58\times {{10}^{-6}}J\text{/}m^{3} $
BETA
