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8.Electromagnetic waves
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The magnetic field in a plane electromagnetic wave is given by $=2 \times 10^{-7} \sin \left(0.5 \times 10^3 x+1.5 \times 10^{11} t\right)$. This electromagnetic wave is .........
A
Visible light
B
Infrared
C
Microwave
D
Radiowave
Solution
(d)
$B=2 \times 10^{-7} \sin \left(0.5 \times 10^{-3} x+1.5 \times 10^{11} t\right)$
$f=\frac{c}{\lambda}, \quad k=0.5 \times 10^{-3}$
$\omega=1.5 \times 10^{11}$
$V=\frac{\omega}{k}=\frac{1.5 \times 10^{11}}{0.5 \times 10^{-3}}=3 \times 10^{14}$
$\frac{\omega}{k}=f \lambda$
$k=\frac{2 \pi}{\lambda}$
$\therefore \lambda= \frac{2 \pi}{k}=\frac{2 \times 22}{7 \times 0.5 \times 10^{-3}}={1.25 \times 10^4} \,m$
Standard 12
Physics
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