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Question
The intensity of the sunlight reaching Earth is 1380 W m−2. Assume this light to be a plane, monochromatic wave. Find the amplitudes of electric and magnetic fields in this wave.
Solution
Given :
`I = 1380 "W/m"^2`
`I = 1/2 ∈_0 E_0^2 c`
⇒ `E_0 = sqrt((2I)/(∈_0c)`
⇒ `E_0 = sqrt((2 xx 1380)/(8.83 xx 10^-12 xx 3 xx 10^8))`
⇒ `E_0 = 103.95 xx 10^4`
⇒ `E_0 = 10.195 xx 10^2`
⇒ `E_0 = 1.02 xx 10^3 "N/C"`
Since `E_0 = B_0c` ,
`B_0 = (E_0)/c = (1.02 xx 10^2)/(3 xx 10^28)`
⇒ `B_0 = 3.398 xx 10^-6`
⇒ `B_0 = 3.4 xx 10^-6 "T"`
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