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8.Electromagnetic waves
hard
Equation of light wave, normally incident on a surface is $B = \left( {100nT} \right)\sin (2\pi ({10^{15}}t - \left( {3 \times {{10}^{ - 7}}} \right)x) + \frac{\pi }{6})$ .Find intensity of light on that surface ...$W/m^2$
A
$1.2$
B
$1.6$
C
$0.8$
D
$0.9$
Solution
$I=\frac{B_{0}^{2}}{2 \mu} \times C$
$I=\frac{(100)^{2} \times\left(10^{-9}\right)^{2}}{2 \times 4 \pi \times 10^{-7}} \times 3 \times 10^{8}$
$I=\frac{10^{4} \times 10^{-18} \times 3 \times 10^{8}}{8 \pi \times 10^{-7}}$
$I=\frac{30}{89}=1.19426$
Standard 12
Physics
