Question

An electric field of an EM wave is given by: E = 50 cos (108t + Bry What direction is the magnetic field going to be in? -X +z -y +y -Z +x

Answer 1

According to the Right Hand Rule to determine the direction of position vector from the directions of the Electric and the Magnetic fields, the direction of position vector will be in the direction of E X B [Electric field vector direction cross product with magnetic field vector direction].

Eg:

Let the Electric field vector is in the direction of +y and the magnetic field in the direction of +z, then the position vector direction will be in (+y) X (+z) =+x direction.

Similarly with this rule, we can find the direction of any vector of the electric field, magnetic field, and position vector provided if the directions of other two vectors are given.

Eg:

Let the Magnetic field vector direction is in +x and the position vector direction is in +y, then the position vector of the electric field will be -z, since (-z) X (+y) =+x.

Now let's go to our problem, given the electric field vector is E=50 cos(10⁸t+ßx) y^{^}. i.e. from this equation it is clear that the electric field is in +y direction and the position vector is in +x direction. So, the position vector of magnetic field will be in the direction of (+z), since (+y) X (+z) = +x.

Therefore, the direction of the magnetic field is in (+z) direction.