Suma de fuerzas : 7N y 5N = 3N La fuerza resultante es :
no llego a entender cual es la formula :(

The direction of an EM wave's Poynting vector determines the direction of the wave's propagation:

S = 1/μ₀(E×B)

S is the Poynting vector, μ₀ is the magnetic constant, E is the electric field vector, and B is the magnetic field vector. Note that we are taking the cross product between E and B, not taking the product of two scalar quantities.

Since S depends on the cross product of E and B, you may use the right hand rule in the following way to determine the direction of B:

The EM wave travels in the +y direction, therefore S points in the +y direction. Face your palm in the +y direction.E points along the z axis. Let us arbitrarily choose +z. Point your thumb in the +z direction.This will constrain your other fingers to point in the +x direction. If you point your thumb in the -z direction then your fingers will point in the -x direction.

You can conclude that B must point along the x axis.