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PRINCIPLES AND LAWS OF DIFFRACTION
HUYGENS PRINCIPLE
A Dutch physicist Christiaan Huygens earlier proposed in 1678, that "every point in which a luminous disturbance reaches act as a source of a wave spherical in nature", the summation of this secondary waves determines the form of the wave at any point in time".
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Recall that, AB = d sinθ
Thus
nλ = 2.d.sinθ
APPLICATION OF DIFFRACTION
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Here are some of the applications of diffraction
SCIENTIFIC APPLICATION
- Diffraction is used a lot in discovering the structures of materials and atoms.
- It has been used a lot in discovering medicines and drugs.
- Diffraction is also fundamental in other applications such as x-ray diffraction studies of crystals and holography* {}SCIENTIFIC APPLICATION DAY TO DAY APPLICATION*
The effects of diffraction are usually seen in everyday life. One of the most evident examples of diffraction are those involving light; for example,when you take a keen look at a CD or DVD the closely spaced tracks on a CD or DVD act as a diffraction grating to form the familiar rainbow pattern. This principle can be extended to engineer a grating with a structure such that it will produce any diffraction pattern desired;
the hologram on a credit card.
DIFFRACTION GRATING
A diffraction grating may be either a transmission grating (a plate pierced with small, parallel, evenly spaced slits through which light passes) or a reflection grating (a plate of metal or glass that reflects light from polished strips between parallel lines ruled on its surface). In the case of a reflection grating, the smooth surfaces between the lines act as narrow slits. The number of these slits or lines is often 12,000 or more to the centimeter (30,000 to the inch). The ruling is generally done with a fine diamond point. Since the light diffracted is also dispersed (spectrum), these gratings are utilized in diffraction spectroscopes for producing and analyzing spectra and for measuring directly the wavelengths of lines appearing in certain spectra. The diffraction of X rays by crystals is used to examine the atomic and molecular structure of these crystals. Beams of particles can also exhibit diffraction since, according to the quantum theory, a moving particle also has certain wavelike properties. Both electron diffraction and neutron diffraction have been important in modern physics research. Sound waves and water waves also undergo diffraction.
APPLICATION OF DIFFRACTION GRATING
Difraction gratings have several applications. Some of the applications includes:
1.SPECTROMETERS (devices which measure properties of light), MONOCHROMATORS (devices which only transmit rather narrow ranges of wavelengths of ELECTROMAGNETIC radiation chosen from sources which provide a greater range of wavelengths)
2.It's Application is also imminent in fibre optic communication (wavelength division multiplexing, to be more specific, which allows different wavelengths of light to carry different signals over a single strand of the optical fibre).
3.Hologram (holos--whole: gram--message) can be imagined as a complicated diffraction grating. The recording of a hologram involves the mixing of a laser beam and the unfocused diffraction pattern of some object. In order to reconstruct an image of the object (holography is also known as wavefront reconstruction) an illuminating beam is diffracted by plane surfaces within the hologram, following Bragg's Law, such that an observer can view the image with all of its three-dimensional detail.
Read more: Diffraction - Fundamentals, Applications - Aperture, Light, Pattern, and Waves - JRank Articles http://science.jrank.org/pages/2063/Diffraction.html#ixzz2FDjBUAeX
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