Holography is an upcoming field in physics related technologies and holds promises in data storage. Holography is based upon principles of optics like intereference.
The basic difference between photography and holography is that while in a photograph, only the information about the intensity distribution of light at different points in the area being photographed is recorded, in holography, the information about the phase of light is also recorded. This gives a three-dimensional image which resembles the object.
Showing posts with label Optics. Show all posts
Showing posts with label Optics. Show all posts
Thursday, January 05, 2006
Applications of Optics
Optics and Optical phenomena find many examples in nature such as the formation of the rainbow, the phenomenon of mirage and twinkling of stars. There are many other applications of optics using lens systems, mirrors, lasers and diffraction gratings etc. Many beautiful experiments can be designed in Optics and put to various uses.
The field of ray optics is used to design and use the Microscope, the Telescope and cameras. There are various designs of the microscope which give different levels of magnification and resolution. The telescope, similary has different types of designs. Optics is also used in the design of precision components and systems. Precise instruments are important in machine design and testing.
Other applications include using spectrometers to analyze the spectrum of a source, and hence to deduce its characteristics. This method is called spectroscopy. Spectroscopy can be used to analyze the atomic structure of atoms, or the composition if a source.
The field of fiber optics is advanced and still a large amount of research is going on in fiber optics. This field is useful in communication systems. Fibers form the backbone of many communication systems.
Hologrpahy is yet another field of optics which holds promises in data storage.
The field of ray optics is used to design and use the Microscope, the Telescope and cameras. There are various designs of the microscope which give different levels of magnification and resolution. The telescope, similary has different types of designs. Optics is also used in the design of precision components and systems. Precise instruments are important in machine design and testing.
Other applications include using spectrometers to analyze the spectrum of a source, and hence to deduce its characteristics. This method is called spectroscopy. Spectroscopy can be used to analyze the atomic structure of atoms, or the composition if a source.
The field of fiber optics is advanced and still a large amount of research is going on in fiber optics. This field is useful in communication systems. Fibers form the backbone of many communication systems.
Hologrpahy is yet another field of optics which holds promises in data storage.
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Birefringence
In an isotropic medium, the velocity of propagation of light is independent of the direction of propagation. However, in anisotropic media, the velocity depends upon the direction in which light is propagating. Also, it depends upon its state of polarization.
In general, when light rays enter such an anisotropic medium, they split up into two rays which have orthogonal polarization. They propagate along different directions. This phenomenon of one light ray giving rise to two refracted rays is called double refraction or birefringence.
One of these rays is called an ordinary ray, while the other is called an extraordinary ray. The ordinary ray follows Snell's laws of refraction while the extraordinary ray does not. The ordinary ray has the same velocity along all directions of propagation, while the the velocity of the extraordinary ray depends upon the direction of propagation.
There can be one or two directions in the crystal in which the velocities of the ordinary and the extraordinary are the same. If there is only one such direction, the crystal medium is called an uniaxial medium. If there are two such directions, it is called a biaxial medium. Quartz is an example of an uniaxial medium, while borax is a biaxial medium.
This phenomenon is useful in making polarization devices such as wave plates, and in non-linear optical applications such as second harmonic generation, sub-harmonic generation and parametric amplification.
Introduction to Optics
Optics deals with the phenomena associated with light. Optics has different realms in which light can have different models. To say this means that light can be treated as -
- A stream of fast moving classical particles, or
- a wave (electromagnetic wave), or
- A collection of chunks of energy called photons (which are quantum particles).
Ray Optics
Interaction of light with lenses is part of a branch known as ray optics. Here since the size of the the equipment with which light interacts is large. When I say large, I mean large compared to the wavelength of light, which is rather smaller than ordinary lengths we encounter. Ray optics is used to analyze lens systems in cameras, telescopes, microscoped and similar optical devices. One can explain the formation of rainbows using ray optics, again because the rain drops responsible for a rainbow are much larger than the wavelength of light. Ray optics basically treats light as rays emerging from a source, travelling in straight lines unless disturbed and obeying the laws of reflection and refraction. Phenomena like interference, diffraction aren't treated (these are dealt with in wave optics, and the photon model also explains these with laws of quantum physics). These are phenomena that involve two waves coming together to give either regions brighter than both of them put together, or resulting in regions of darkness.Related Links:
History of Optics
The history of Optics is made interesting by the frequent swings of physicists' viewpoints about whether light is of a wave nature or of a particle nature.
The investigations about the nature of light have made significant contributions to the development of an altogether different branch of physics known as quantum physics, one of the crowning achievements of the physicists of the 20th century.
Isaac Newton, the great physicist, wrote the classic Optiks in which he has given an account of the numerous experiments he performed to study light. He believed light to be a stream of particles or corpuscles. The corpuscular model of light was originally proposed by Descartes. The corpuscular model of light was in tune with Netwon's laws of motion, he believed that these corpusles travel in straight lines when not acted upon by external sources. This explained the rectilinear propagation (i.e. travelling in a straight line) of light. A particle incident upon a plane smooth surface can be shown to have equal values for the angles of incidence and reflection. Thus, the well-known laws of reflection for light on a plane surface could be accounted for by the corpuscle picture. He tried to explain the laws of refraction by assuming that particles of a denser medium attract the corpuscles of light hence causing it to bend at the surface.
Christian Huygens (1629-1695), a Dutch physicist and a contemorary of Newton belived that light was a wave and with the so called "Huygen's Principle", explained the laws of reflection and refraction.
Although the wave picture of light wasn't taken too seriously initially, but in 1801, Thomas Young performed the famous double-slit interference experiment and gave a theoretical explanation using the wave theory. In 1814, Fresnel performed an experiment showing diffraction of light and explained it using the wave picture. He also explained the rectilinear propagation of light using the wave theory.
The wave theory was finally widely accepted after Foucault showed that the speed of light is less in water than in air, while Newton's particle-picture suggested that the speed of light should increase in a medium for refraction to take place.
Further, in the year 1857, Maxwell gave the famous Maxwell's equations of electromagnetism. From these laws, he could derive a wave equation. In such waves, a changing electric field creates a magnetic field and the changing magnetic field, in turn, creates an electric field, and the wave propogates. He called these waves electromagnetic waves. He also derived the speed of such a wave and found that this speed, in vacuum, matched the speed of light known at that time by Kohlrausch and Weber.
With making a statement about "faith in rationality of nature", he gave the electromagnetic theory of light according to which lights is an electromagnetic wave. This was experimentally verified by Heinrich Hertz in 1888.
Isaac Newton, the great physicist, wrote the classic Optiks in which he has given an account of the numerous experiments he performed to study light. He believed light to be a stream of particles or corpuscles. The corpuscular model of light was originally proposed by Descartes. The corpuscular model of light was in tune with Netwon's laws of motion, he believed that these corpusles travel in straight lines when not acted upon by external sources. This explained the rectilinear propagation (i.e. travelling in a straight line) of light. A particle incident upon a plane smooth surface can be shown to have equal values for the angles of incidence and reflection. Thus, the well-known laws of reflection for light on a plane surface could be accounted for by the corpuscle picture. He tried to explain the laws of refraction by assuming that particles of a denser medium attract the corpuscles of light hence causing it to bend at the surface.
Christian Huygens (1629-1695), a Dutch physicist and a contemorary of Newton belived that light was a wave and with the so called "Huygen's Principle", explained the laws of reflection and refraction.
Although the wave picture of light wasn't taken too seriously initially, but in 1801, Thomas Young performed the famous double-slit interference experiment and gave a theoretical explanation using the wave theory. In 1814, Fresnel performed an experiment showing diffraction of light and explained it using the wave picture. He also explained the rectilinear propagation of light using the wave theory.
The wave theory was finally widely accepted after Foucault showed that the speed of light is less in water than in air, while Newton's particle-picture suggested that the speed of light should increase in a medium for refraction to take place.
Further, in the year 1857, Maxwell gave the famous Maxwell's equations of electromagnetism. From these laws, he could derive a wave equation. In such waves, a changing electric field creates a magnetic field and the changing magnetic field, in turn, creates an electric field, and the wave propogates. He called these waves electromagnetic waves. He also derived the speed of such a wave and found that this speed, in vacuum, matched the speed of light known at that time by Kohlrausch and Weber.
With making a statement about "faith in rationality of nature", he gave the electromagnetic theory of light according to which lights is an electromagnetic wave. This was experimentally verified by Heinrich Hertz in 1888.
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