what is defraction?

[Peter Abrahams]

What is defraction, of visible light? Is is relevant to optical
instruments?
I don't find the term in the index of quite a few books on optics.
On line, in addition to scores of hits based on misspelled 'diffraction', I
find:
Defraction of radio waves happens in the atmosphere when the earth absorbs
radio energy, causing tilt of the wavefront (?)
Defraction of light happens in silicon, and is dependent on bandpass (?)
thanks for any assistance.
--Peter Abrahams telscope.at.europa.com
The history of the telescope and the binocular:
http://home.europa.com/~telscope/binotele.htm

[Brian Blandford]

Post by Peter Abrahams
What is defraction, of visible light? Is is relevant to optical
instruments?

It's a misspelling of diffraction, through confusion with "refraction".
Brian

[Repeating Rifle]

Post by Peter Abrahams
What is defraction, of visible light? Is is relevant to optical
instruments?

It is how much light gets through a window divided by how much a incident.
It should not be confused with diffractrion.

Bill

[Don Stauffer]

Diffraction effects are known as physical optics effects, rather than
geometrical optics effects.

They are due to the finite wavelength of light and of apertures. It is
also due to wave nature of light, which can cause interference between
waves 'diffracted' from various parts of an aperture. It sets limits to
how well you can focus a light beam even if all geometrical lens
abberations were reduced to zero. It also causes a veiling glare to
cover image when a screen is placed in or near aperture.

Do a search on diffraction, or 'physical optics' in google.

Post by Peter Abrahams
What is defraction, of visible light? Is is relevant to optical
instruments?
I don't find the term in the index of quite a few books on optics.
On line, in addition to scores of hits based on misspelled 'diffraction', I
Defraction of radio waves happens in the atmosphere when the earth absorbs
radio energy, causing tilt of the wavefront (?)
Defraction of light happens in silicon, and is dependent on bandpass (?)
thanks for any assistance.
--Peter Abrahams telscope.at.europa.com
http://home.europa.com/~telscope/binotele.htm

[Optiker857]

The term "Diffraction" is used rather loosely in the world of physics
and optics to mean either of two things.

The first is effect of a boundary that changes the spatial
distribution of the phase and/or amplitude of light waves. Examples
abound for the knowledgeable observer. Examples include the
distribution of light waves following a lens, peering at a small
angular source through a hair comb, and etc. This first definition
describes the effects of the "wave-nature of light" that are not
accounted for using a ray description of light. The shorter the
wavelength of the light wave, the more "ray-like" the wave behaves.
Hence, in the context of this first definition "diffraction" is also
used as a quantitative description of light rahter than as a
phenomological one. Light under one set of circumstances may
experience more "diffraction" than under other circumstances.

The second definition, which is more accurate and detailed, deals with
how light behaves if only its wave nature is considered. There are
descriptions that deal woth diffraction using ray descriptions of
light, but we can ignore those for now. In this context, diffraction
deals with how light propagates, travels, or evolves as a function of
space and time. In this sense "diffraction" is a mathematical
formalism that is a solution to the wave equation derived from
Maxwell's equations. Hence, this second definition is a more
phenomological one. It is in this context that I like to think of
diffraction.

There is an excellent description of diffraction, using both these
descriptions in Hecht's book, called "Optics".

I hope this helps.