Em Waves Question 141
Question: The energy contained in a cylinder of cross- section $ 10cm^{2} $ and length 50cm along the x-axis if electric field in an electromagnetic wave is given by $ E=50,\sin ,\omega (t-x/c) $ is
Options:
A) $ 1.2\times {{10}^{-10}},J $
B) $ 5.5\times {{10}^{-12}},J $
C) $ 2.3\times {{10}^{-10}},J $
D) $ 3.6\times {{10}^{-12}},J $
Show Answer
Answer:
Correct Answer: B
Solution:
[b] Energy density $ =\frac{1}{2}{\varepsilon _{0}}E _{0}^{2}=1.1\times {{10}^{-8}},J,{{m}^{-3}} $ Volume of cylinder $ =A\times L=5\times {{10}^{-4}}m^{3} $ So, required energy $ =1.1\times {{10}^{-8}}\times 5\times {{10}^{-4}} $
$ =5.5\times {{10}^{-12}}J $
BETA
