The Physics
Hypertextbook
Opus in profectus

# Interference and Superposition

## Summary

• are material, tangible, corporeal, and definite
• cannot occupy the same place at the same time
• exchange energy and momentum during collisions
• Waves
• are immaterial, intangible, incorporeal, and indefinite
• can occupy the same place at the same time
• pass through each other without effect
• Principle of Linear Superposition
• When waves occupy the same place at the same time they interfere or superpose.
• The resulting disturbance is the sum of the individual disturbances at every point in space and time.
• Phase (ϕ)
• The stage of development of a periodic process.
• Two points on a wave with the same phase have the same…
• quantity of disturbance (ex. displacement) and
• rate of change of disturbance (ex. velocity).
• Phase is an angular quantity.
• Adjacent points in phase are separated by one complete cycle (360°).
• Adjacent points out of phase are separated by half a cycle (180°).
• The SI unit of phase is the radian, which is itself a unitless ratio [rad = m/m = Pa/Pa = (V/m)/(V/m) = etc.].
• Range of interference
• Constructive interference occurs when two waves meet with the same phase (in phase) and a maximum amplitude results.
• Destructive interference occurs when two waves meet with opposite phase (out of phase) and a minimum amplitude results.