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.

Answer 1

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"`