Interference of light is a phenomenon in which multiple light waves interact with one another under certain circumstances, causing the combined amplitudes of the waves to either increase or decrease
. This occurs when the distribution of energy due to one wave is disturbed by the other, and the resulting wave has a lower, higher, or the same amplitude as the individual waves
. There are two main types of interference:
- Constructive interference : In this case, the amplitude of the resultant wave at a given position or time is greater than that of either individual wave
- Destructive interference : Here, the amplitude of the resultant wave at a given position or time is smaller than that of either individual wave, and the combined wave may even appear as a dark area (blackness)
Interference of light can be observed in various real-world examples, such as the soap bubble that reflects a variety of colors when light waves interact with the soap's surface
. Another example is the double-slit experiment, which demonstrates the interference of light waves when they pass through two slits and interact with each other
. Interference of light requires the following conditions to be met
:
- The sources of light must emit continuous waves of the same wavelength and time period, and they should have phase coherence.
- The sources of light should be very close to each other.
- The waves emitted by the sources should either have zero phase difference or no phase difference.
In order to observe interference in light waves, the sources must be coherent, meaning they must maintain a constant phase with respect to each other
. In everyday life, most light sources, such as incandescent bulbs, generate a wide range of frequencies of light, including all colors of the rainbow, but they are incoherent, meaning their emissions do not maintain a constant phase relationship with each other over time
. This is why interference effects are not observed with ordinary light sources, and special devices like lasers or interferometers are used to demonstrate interference
