The electric field in a plane electromagnetic wave is given by
$$\overrightarrow E = 200\cos \left[ {\left( {{{0.5 \times {{10}^3}} \over m}} \right)x - \left( {1.5 \times {{10}^{11}}{{rad} \over s} \times t} \right)} \right]{V \over m}\widehat j$$. If this wave falls normally on a perfectly reflecting surface having an area of 100 cm2. If the radiation pressure exerted by the E.M. wave on the surface during a 10 minute exposure is ${x \over {{{10}^9}}}{N \over {{m^2}}}$. Find the value of x .
Answer (integer)
354
Solution
E<sub>0</sub> = 200<br><br>$I = {1 \over 2}{\varepsilon _0}E_0^2.C$<br><br>Radiation pressure<br><br>$P = {{2I} \over C}$<br><br>$= \left( {{2 \over C}} \right)\left( {{1 \over 2}{\varepsilon _0}E_0^2C} \right)$<br><br>$= {\varepsilon _0}E_0^2$<br><br>$= 8.85 \times {10^{ - 12}} \times {200^2}$<br><br>$= 8.85 \times {10^{ - 8}} \times 4$<br><br>$= {{354} \over {{{10}^9}}}$
About this question
Subject: Physics · Chapter: Electromagnetic Waves · Topic: Properties of EM Waves
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