The ratio of contributions made by the eletric field and magnetic field components to the intensity of an `EM` wave is.

Options

A. `c: 1`
B. `c^2 :1`
C. `1:1`
D. `sqrt(c ) : 1`

Answer

C

Explanation

Intensity of an EM wave is given by ` I=U_(av) C` where `U_(av ) = ` average energy carried by an EM wave average energy of EM wave due to electric field is
` (U_(av ) ) e=1/2 epsi_0 E_(0)^(2)`
where `E_0` = amplitude of electric field vector Average of EM wave due to amgnetic field is
` (U_(av ))_B = 1/2 (B_0)^(2))/( mu_0)`
where ` B_0 ` = amplitude of magentic field vector
`(U_(av))_E =1/2 epsi_0 E_0 ^(2) 1/2 epsi_0 (cB_0)^2`
` =1/2 epsi_0 c^2 B_(0)^(2) `
`=1/2 epsi_0 ((1)/(mu_0 epsi_0 )) B_0 ^(2) = 1/2 epsi_0 ((1)/(mu_0 epsi_0 ))B_0 ^(2) = 1/2 (B_0^2 )/(mu_0 ) = (U_(av) )_B`
` therefore ` THe energy carried by EM wave is divided equally between electric field vector and magnetic field vector .