• In general terms, a centreline is a real or imaginary line that passes through the centre of something, often dividing the object into two halves.
  • In a wave diagram used to illustrate electromagnetic waves, a centreline may be used to show either:
    • Point of intersection: This is the ideal centerline and represents the point where the electric and magnetic fields cross zero simultaneously. This point stays constant as the wave propagates.
    • Halfway between crest and trough: This is a common but simpler representation used for ease of visualization. It doesn’t always coincide with the point of field intersection in certain wave types or when considering polarization.