This is a wave in which the displacement is at right angles to the wave direction. Examples are vibrating strings, water waves, radio and television waves. In this type of wave the displacement is in the same direction as the wave direction.
Examples are sound waves in solids, liquids and gases.
The amplitudes add. The amplitudes subtract. Beats The beat frequency when two frequencies f 1 and f 2 are combined together is the difference frequency f 1 - f 2 . Positions of maximum displacement are called antinodes.