A sinusoidal electromagnetic wave is propagating in vacuum in the +z-direction. If at a particular instant and at a certain point in space the electric field is in the +x-direction and has magnitude 3.20 V/m, what are the magnitude and direction of the magnetic field of the wave at this same point in space and instant in time?

The magnitude of the magnetic field is

 The direction is in the +y direction

Explanation:

    From the question we are told that  

      The electric field is

The relationship between electric and magnetic field is mathematically represented  as

Where  c is the speed of light

              is the magnetic field

Making  the subject off the formula

Generally in an electromagnetic wave the direction of the wave propagation , the electric field and the magnetic field are perpendicular

   Since from the question the direction of the electric field is +x direction and the  wave  propagation is in the + z direction then the magnetic field would be in the + y direction