Due to its wave–particle duality, light can exhibit properties of both waves and particles. The study of light, known as optics, is an important research area in modern physics.
Interference is the addition (superposition) of two or more waves that results in a new wave pattern.
Huygens–Fresnel principle - (named for Dutch physicist Christiaan Huygens, and French physicist Augustin-Jean Fresnel) is a method of analysis applied to problems of wave propagation (both in the far field limit and in near field diffraction). It recognizes that each point of an advancing wave front is in fact the center of a fresh disturbance and the source of a new train of waves; and that the advancing wave as a whole may be regarded as the sum of all the secondary waves arising from points in the medium already traversed. This view of wave propagation helps better understand a variety of wave phenomena, such as diffraction.
For example, if two rooms are connected by an open doorway and a sound is produced in a remote corner of one of them, a person in the other room will hear the sound as if it originated at the doorway. As far as the second room is concerned, the vibrating air in the doorway is the source of the sound. The same is true of light passing the edge of an obstacle, but this is not as easily observed because of the short wavelength of visible light.
Huygens principle mathematically follows from the fundamental postulate of quantum electrodynamics – that wavefunctions of every object propagate over any and all allowed (unobstructed) paths from the source to the given point. It is then the result of interference (addition) of all path integrals that defines the amplitude and phase of the wavefunction of the object at this given point, and thus defines the probability of finding the object (say, a photon) at this point. Not only light quanta (photons), but electrons, neutrons, protons, atoms, molecules, and all other objects obey this simple principle.
Photoelectric effect is a quantum electronic phenomenon in which electrons are emitted from matter after the absorption of energy from electromagnetic radiation such as x-rays.[1] The emitted electrons can be referred to as photoelectrons in this context. The effect is also termed the Hertz Effect[2][3], due to its discovery by Heinrich Rudolf Hertz, although the term has generally fallen out of use.
Study of the photoelectric effect led to important steps in understanding the quantum nature of light and electrons and influenced the formation of the concept of wave–particle duality.[1]
Specular reflection is the perfect, mirror-like reflection of light (or sometimes other kinds of wave) from a surface, in which light from a single incoming direction (a ray) is reflected into a single outgoing direction. Such behaviour is described by the law of reflection, which states that the direction of incoming light (the incident ray), and the direction of outgoing light reflected (the reflected ray) make the same angle with respect to the surface normal, thus the angle of incidence equals the angle of reflection; this is commonly stated as θi = θr.
This is in contrast to diffuse reflection, where incoming light is reflected in a broad range of directions. The most familiar example of the distinction between specular and diffuse reflection would be matte and glossy paints. While both exhibit a combination of specular and diffuse reflection, matte paints have a higher proportion of diffuse reflection and glossy paints have a greater proportion of specular reflection. Very highly polished surfaces, such as high quality mirrors, can exhibit almost perfect specular reflection.
Even when a surface exhibits only specular reflection with no diffuse reflection, not all of the light is necessarily reflected. Some of the light may be absorbed by the materials. Additionally, depending on the type of material behind the surface, some of the light may be transmitted through the surface. For most interfaces between materials, the fraction of the light that is reflected increases with increasing angle of incidence θi. If the light is propagating in a material with a higher index of refraction than the material whose surface it strikes, then total internal reflection may occur. Specular reflection from a dielectric such as water can affect polarization and at Brewster's angle reflected light is completely linearly polarized parallel to the interface.
The law of reflection arises from diffraction of a plane wave (with small wavelength) on a flat boundary: when the boundary size is much larger than the wavelength then electrons of the boundary are seen oscillating exactly in phase only from one direction — the specular direction. If a mirror becomes very small (comparable to the wavelength), the law of reflection no longer holds and the behaviour of light is more complicated.
Usually, the term specular reflection refers to visible light; however the term specular reflection is also widely used in technology and science for other electromagnetic waves. The specular reflection of non-electromagnetic waves follows basically the same laws. There exist acoustical mirrors and even atomic mirrors, which provide the specular reflection of neutral atoms. For the efficient reflection of atoms from a solid-state mirror, very cold atoms and/or grazing incidence are used in order to get significant quantum reflection. The ridged mirrors are used to enhance the specular reflection of atoms.
Diffuse reflection is the reflection of light from an uneven or granular surface such that an incident ray is seemingly reflected at a number of angles. It is the complement to specular reflection. If a surface is completely nonspecular, the reflected light will be evenly spread over the hemisphere surrounding the surface (2×π steradians).
The most familiar example of the distinction between specular and diffuse reflection would be matte and glossy paints as used in home painting. Matte paints have a higher proportion of diffuse reflection, while gloss paints have a greater part of specular reflection.
Diffuse interreflection is a process whereby light reflected from an object strikes other objects in the surrounding area, illuminating them. Diffuse interreflection specifically describes light reflected from objects which are not shiny or specular. In real life terms what this means is that light is reflected off non-shiny surfaces such as the ground, walls, or fabric, to reach areas not directly in view of a light source. If the diffuse surface is colored, the reflected light is also colored, resulting in similar coloration of surrounding objects.
In 3D computer graphics, diffuse interreflection is an important component of global illumination. There are a number of ways to model diffuse interreflection when rendering a scene. Radiosity and photon mapping are two commonly used methods.
MY SOURCE - www.Wikipedia.com and my notes
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