Constructive Interference

Constructive interference is demonstrated with single transverse pulses in a Slinky™.

Discussion

Interference, both constructive and destructive, is a phenomenon common to all types of waves, and is a fundamental characteristic that distinguishes waves from particles. In this movie we show constructive interference in transverse waves. When wave pulses traveling in opposite directions on a Slinky™ pass each other they interfere constructively (displacements adding) when their peaks are on the same side of the Slinky™. This is an example of the principle of superposition, a property of waves: when two or more waves overlap, the resultant wave disturbance is the algebraic sum of the individual wave disturbances.

By stepping carefully through this movie during the period when the two pulses are passing each other, you can show that the amplitude, or maximum displacement, of the combined wave pulse at the point of maximum overlap is equal to the sum of the amplitudes of the two single pulses.