The intensity of the sunlight reaching the earth is 1380 Wm^-2. Calculate the amplitudes of electric and magnetic field in the light wave. Assume the light to be a plane monochromatic wave.

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Solution

Given,
Intensity of sunlight, I = 1380 Wm^-2Intensity of plane monochromatic wave,

I = \frac{1}{2} ε_{0} E_{0}^{2} c

Using the formula,
Magnitude of electric field,

E_{0} = \sqrt{\frac{2 I}{ε_{0} c}}

\Rightarrow E_{0} = \sqrt{\frac{2 \times 1380}{8.85 \times 10^{- 12} \times 3 \times 10^{8}}} {NC}^{- 1}

= 1.02 \times 10^{3} {NC}^{- 1} .

Amplitude of magentic field,

B_{0} = \frac{E_{0}}{c}

= \frac{1.02 \times 10^{3}}{3 \times 10^{8}} T = 3.4 \times 10^{- 6} T = 3.4 μT .

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