A fringe wave, more accurately referred to as an interference fringe, is an alternating band of light and dark (or varying intensities of light) formed due to the interference of two or more light waves.
This phenomenon occurs when waves from coherent sources (sources that emit waves with a constant phase relationship) superimpose. The resulting pattern is a series of fringes, which are regions of constructive and destructive interference.
Here's a more detailed breakdown:
-
Constructive Interference: When the waves arrive in phase (crests aligned with crests, and troughs with troughs), they reinforce each other, resulting in a bright fringe.
-
Destructive Interference: When the waves arrive out of phase (crests aligned with troughs), they cancel each other out, resulting in a dark fringe.
The spacing between these fringes, called the fringe width (β), depends on several factors, including:
- Wavelength of light (λ): Longer wavelengths produce wider fringes.
- Distance between the source and the screen (D): Greater distances result in wider fringes.
- Distance between the two slits (d): Smaller distances between the slits result in wider fringes.
The fringe width can be calculated using the following formula:
β = λD / d
Where:
- β is the fringe width
- λ is the wavelength of the light
- D is the distance between the source and the screen
- d is the distance between the two slits.
Fringe patterns are observed in various optical phenomena, such as:
- Young's Double Slit Experiment: A classic demonstration of wave interference, where light passing through two narrow slits creates an interference pattern on a screen.
- Thin Films: Interference of light reflected from the top and bottom surfaces of a thin film (e.g., an oil slick) creates colorful fringes.
- Interferometers: Instruments that use interference to measure distances, refractive indices, and other physical properties with high precision.
