The principle of superposition in the context of interference states that when two or more light waves overlap at a point, the resulting wave is the sum of their individual electric field amplitudes at that point.
In simpler terms:
- Light behaves as a wave, with peaks (crests) and valleys (troughs).
- When waves meet, their effects combine—either adding up or canceling out depending on how their peaks and troughs align.
This leads to two main outcomes:
- Constructive Interference:
- Occurs when the waves are in phase (crests with crests, troughs with troughs).
- Their amplitudes add up, producing brighter light.
- Destructive Interference:
- Happens when the waves are out of phase (a crest meets a trough).
- Their amplitudes cancel out, leading to darkness or reduced intensity.
The superposition principle is what explains the formation of interference patterns, such as the bright and dark fringes seen in Young’s double-slit experiment. It confirms that light has wave-like properties, as only waves can combine in this way.