As shown in the given diagram the field pattern of electromagnetic waves is such that electric field is perpendicular to the magnetic field and both the fields are perpendicular to the direction of propagation.
The field pattern diagram no. 1 explains the further characteristics of electromagnetic field. Looking towards the field when it is propagated from the source it follows the pattern of the positive half cycle. It means that the electric field keeps on increasing from the reference point and after its maximum amplitude it comes back to its reference point again for the next half cycle. The behavior of electric field is the same but in opposite direction. In this way the electric field travels from source to load.
Looking towards the magnetic field of the diagram, it is very clear that the behavior of the magnetic field is exactly the same as for the electric field. But they remain perpendicular to each other.
If we consider the direction of propagation, we can come to know that while keeping themselves perpendicular to each other, the electric and magnetic fields are also perpendicular to the direction of propagation.
As shown in the given diagram no. 3 of electromagnetic field pattern for the dipole antenna, it is indicated that if the dipole antenna is mounted horizontally its electric field will also be horizontally polarized.
Looking towards the diagram no. 3 it is indicated that magnetic field H-field in circles the arms of the dipole and perpendicular to the E-field.