Interference pattern of two slits illuminated with white light
A phenomenon in which two waves superimpose to form a resultant wave of greater or lower amplitude.
Interference usually refers to the interaction of waves that are correlated or coherent with each other, either because they come from the same source or because they have the same or nearly the same frequency.
If a crest of one wave meets a trough of another wave then the magnitude of the displacements is equal to the difference in the individual magnitudes – this is known as destructive interference. Constructive interference occurs when the phase difference between the waves is a multiple of 2π, whereas destructive interference occurs when the difference is an odd multiple of π. If we let light pass through two slits simultaneously, beautiful dark and light band, called interference fringes, can be observed.
The Double–slit experiment is a demonstration that matter and energy can display characteristics of both waves and particles, and demonstrates the fundamentally probabilistic nature of quantum mechanical phenomena.
Newton's rings
Newton's Rings :
The phenomenon of Newton's rings is an interference pattern caused by the reflection of light between two surfaces – a spherical surface and an adjacent flat surface. When viewed with monochromatic light it appears as a series of concentric, alternating light and dark rings centered at the point of contact between the two surfaces. When viewed with white light, it forms a concentric ring pattern of rainbow colors because the different wavelengths of light interfere at different thicknesses of the air layer between the surfaces. The light rings are caused by constructive interference between the light rays reflected from both surfaces, while the dark rings are caused by destructive interference.
The center of Newton's ring is always dark because there are NO constructive interference and also because that is the point of contact between the two surfaces. How far from the center do the light interfere constructively and destructively is determined by the wavelength of the light.