Superposition of Pulses
Superposition of Pulses
Two or more pulses can pass through the same medium at that same time in the same place. When they do they interact with each other to form a different disturbance at that point. The resulting pulse is obtained by using the principle of superposition.
Definition: Principle of superposition
The principle of superposition states that when two disturbance occupy the same space at the same time the resulting disturbance is the sum of two disturbances.
After pulses pass through each other, each pulse continues along its original direction of travel, and their original amplitudes remain unchanged.
Constructive interference takes place when two pulses meet each other to create a larger pulse. The amplitude of the resulting pulse is the sum of the amplitudes of the two initial pulses. This could be two crests meeting or two troughs meeting. This is shown in the figure below.
Definition: Constructive interference
Constructive interference is when two pulses meet, resulting in a bigger pulse.
Superposition of two pulses: constructive interference.
Destructive interference takes place when two pulses meet and result in a smaller amplitude disturbance. The amplitude of the resulting pulse is the sum of the amplitudes of the two initial pulses, but the one amplitude will be a negative number. This is shown in the figure below. In general, amplitudes of individual pulses are summed together to give the amplitude of the resultant pulse.
Definition: Destructive interference
Destructive interference is when two pulses meet, resulting in a smaller pulse.
Superposition of two pulses. The left-hand series of images demonstrates destructive interference, since the pulses cancel each other. The right-hand series of images demonstrate a partial cancellation of two pulses, as their amplitudes are not the same in magnitude.
This lesson is part of:
Mechanical Waves and Sound