How are interference fringes formed in light waves?

Interference fringes in light waves are formed due to the superposition of two or more coherent light waves.

Interference is a fundamental concept in wave physics, including light which is an electromagnetic wave. When two or more waves meet, they interact with each other. This interaction can either amplify or diminish the resultant wave, depending on the phase difference between the waves. This phenomenon is known as superposition. When this occurs with light waves, it can result in the formation of interference fringes.

The formation of interference fringes is best explained using the double-slit experiment. In this experiment, a light source is shone through two closely spaced slits. The light waves from the two slits then overlap and interfere with each other. If the waves arrive in phase (i.e., the peaks and troughs align), they will constructively interfere, resulting in a bright fringe. Conversely, if the waves arrive out of phase (i.e., a peak aligns with a trough), they will destructively interfere, resulting in a dark fringe. This pattern of bright and dark fringes is known as an interference pattern.

The key to the formation of interference fringes is the coherence of the light source. Coherent light waves have a constant phase difference, which is necessary for the formation of a stable interference pattern. In the double-slit experiment, the light source is split into two coherent waves by the slits. As these waves propagate and overlap, they create an interference pattern of fringes.

The position and spacing of the fringes depend on several factors, including the wavelength of the light, the distance between the slits, and the distance from the slits to the screen where the fringes are observed. By analysing the interference pattern, these parameters can be determined, making interference a powerful tool in physics.

In conclusion, interference fringes in light waves are a fascinating demonstration of the wave nature of light. They are formed due to the superposition of coherent light waves, resulting in a pattern of bright and dark fringes.