A plane electromagnetic wave of wavelength `lambda` has an intensity I. It is propagating along the positive Y-direction. The allowed expression for the electric and magnetic fields ar given by :

Options

A. `vecE = sqrt((2I )/( epsi_0 C )) cos [ ( 2pi )/( lamda ) ( y- c t ) ] hatk , vecB = + 1/C E hati`
B. `vecE = sqrt((I )/( epsi_0 C )) cos [ (2 pi ) /( lamda) ( y- c t ) ] hatk , vecB = + 1/C E hati`
C. `vecE = sqrt((I )/(epsi_0 C ) ) cos [ ( 2pi ) / ( lamda) ( y- ct ) ] hatk , vecB = 1/C E hati`
D. `vecE = sqrt((I )/(epsi_0 C )) cos [ ( 2 pi ) /( lamda ( y- ct )) ] hatk , vecB = (1)/(C ) e hatk `

Answer

A

Explanation

IF ` E_0 ` is amplitude of electric field then
` 1/2 epsi_0 E_(0)^(2) xx C =I`
` E_0 = sqrt((2I)/( epsi_0 C ))`
direction of propagating wave is positive Y- direction , hence
` vecS = vecE xx vecB ` will be alongs positive Y- direction `( + hatj ) `.
so option (a ) is correct .