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Diffraction Refers To Various Phenomena That Occur When A: History

Diffraction refers to the bending and spreading of waves when they encounter an obstacle or opening. It occurs when a wave passes an object that is comparable in size to the wavelength of the wave. Francesco Grimaldi first coined the term "diffraction" and recorded accurate observations of the phenomenon in 1660. The Huygens-Fresnel principle describes diffraction as each point in a propagating wavefront acting as a spherical wavelet, with the interference of these wavelets producing characteristic banding patterns when waves encounter openings around the size of their wavelength. Diffraction occurs for all types of waves, including light, sound, water waves and quantum particles.

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66 views2 pages

Diffraction Refers To Various Phenomena That Occur When A: History

Diffraction refers to the bending and spreading of waves when they encounter an obstacle or opening. It occurs when a wave passes an object that is comparable in size to the wavelength of the wave. Francesco Grimaldi first coined the term "diffraction" and recorded accurate observations of the phenomenon in 1660. The Huygens-Fresnel principle describes diffraction as each point in a propagating wavefront acting as a spherical wavelet, with the interference of these wavelets producing characteristic banding patterns when waves encounter openings around the size of their wavelength. Diffraction occurs for all types of waves, including light, sound, water waves and quantum particles.

Uploaded by

Azreen Anis azmi
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© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Diffraction refers to various phenomena that occur when a wave encounters an obstacle or a slit.

It
is defined as the bending of waves around the corners of an obstacle or through an aperture into the
region of geometrical shadow of the obstacle/aperture. The diffracting object or aperture effectively
becomes a secondary source of the propagating wave. Italian scientist Francesco Maria
Grimaldi coined the word "diffraction" and was the first to record accurate observations of the
phenomenon in 1660.[1][2]

Infinitely many points (3 shown) along length d project phase contributions from the wave-front, producing a
continuously varying intensity θ on the registering plate.

In classical physics, the diffraction phenomenon is described by the Huygens–Fresnel principle that


treats each point in a propagating wave-front as a collection of individual spherical wavelets.[3] The
characteristic banding pattern is most pronounced when a wave from a coherent source (such as a
laser) encounters a slit/aperture that is comparable in size to its wavelength, as shown in the
inserted image. This is due to the addition, or interference, of different points on the wave-front (or,
equivalently, each wavelet) that travel by paths of different lengths to the registering surface.
However, if there are multiple, closely spaced openings, a complex pattern of varying intensity can
result.
These effects also occur when a light wave travels through a medium with a varying refractive index,
or when a sound wave travels through a medium with varying acoustic impedance – all waves
diffract, including gravitational waves[citation needed], water waves, and other electromagnetic waves such
as X-rays and radio waves. Furthermore, quantum mechanics also demonstrates that matter
possesses wave-like properties, and hence, undergoes diffraction (which is measurable at
subatomic to molecular levels).[4]
Diffraction and interference are closely related and are nearly – if not exactly – identical in
meaning. Richard Feynman observes that "diffraction" tends to be used when referring to many
wave sources, and "interference" when only a few are considered.[5]

History[edit]
Thomas Young's sketch of two-slit diffraction for water waves, which he presented to the Royal Society in
1803.

The effects of diffraction of light were first carefully observed and characterized by Francesco Maria
Grimaldi, who also coined the term diffraction, from the Latin diffringere, 'to break into pieces',
referring to light breaking up into different directions. The results of Grimaldi's observations were
published posthumously in 1665.[6][7][8] Isaac Newton studied these effects and attributed them
to inflexion of light rays. James Gregory (1638–1675) observed the diffraction patterns caused by a
bird feather, which was effectively the first diffraction grating to be discovered.[9] Thomas
Young performed a celebrated experiment in 1803 demonstrating interference from two closely
spaced slits.[10] Explaining his results by interference of the waves emanating from the two different
slits, he deduced that light must propagate as waves. Augustin-Jean Fresnel did more definitive
studies and calculations of diffraction, made public in 1816[11] and 1818,[12] and thereby gave great
support to the wave theory of light that had been advanced by Christiaan Huygens[13] and
reinvigorated by Young, against Newton's particle theory.

Mechanism

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