Download Many other important inventions involve the use of

Chan Medric 3A305
Physics Ace
Many other important inventions involve the use of refraction. Examples are cameras, LASIK operation
procedure etc.
Your job is to research on 5 important technological inventions that worked on the phenomenon of
refraction.
In your research report, include:
- pictures of the inventions
- how they work, using refraction
1．Glasses
Though it is an extremely simple invention, glasses are one of the most important
inventions in physics due to the massive amount of problems they have solved for many
of those who have problems with eyesight. They are mainly made of frames
bearing lenses worn in front of the eyes, normally for vision correction, eye protection,
or for protection from UV rays.
Modern glasses are typically supported by pads on the bridge of the nose and
by temple arms placed over the ears. Eyeglass lenses are commonly made from plastic.
The materials reduce the danger of breakage and weigh less than glass lenses. Some
plastics also have more advantageous optical properties than glass, such as better
transmission of visible light and greater absorption of ultraviolet light. Some plastics
have a greater index of refraction than most types of glass, this is useful in the making
of corrective lenses shaped to correct various vision abnormalities like myopia, allowing
thinner lenses for a given prescription.
Not all glasses are designed solely for vision correction but are worn
for protection, viewing visual information or simply just for aesthetic or
fashion values. Safety glasses are a kind of eye protection against
flying debris or against visible and near
visible light or radiation. Sunglasses allow better vision in bright
daylight, and may protect against damage from high levels of ultraviolet light.
How Glasses Work
For nearsightedness, glasses correct the problem of the eyeball being too long to focus
upon a far away image projected onto the retina. The glasses offer a concave lens that
bends light rays outward, which normalizes the eyeball. In
farsightedness, the eyeball
is too short to focus upon objects that are near. Glasses
use a convex lens that bends the light inward before it
reaches the eye's lens, thereby correcting vision.
History
The earliest historical reference to magnification dates back to ancient
Egyptian hieroglyphs in the 6th century BC, which depict "simple glass meniscal lenses".
The earliest written record of magnification dates back to the 1st century AD,
when Seneca the Younger, a tutor of Emperor Nero who wrote that letters, however
small and indistinct, are seen enlarged and more clearly through a globe or glass filled
with water.
Around 1284 in Italy, Salvino D'Armate is credited with inventing the first wearable eye
glasses. The earliest pictorial evidence for the use of eyeglasses, however, is Tomaso
da Modena's 1352 portrait of the cardinal Hugh de Provence reading in a scriptorium.
Another early example would be a depiction of eyeglasses found north of the Alps in an
altarpiece of the church of Bad Wildungen, Germany, in 1403.
Many theories abound for whom should be credited for the invention of traditional
eyeglasses. In 1676, Francesco Redi, a professor of medicine at the University
of Pisa, wrote that he possessed a 1289 manuscript whose author complains
that he would be unable to read or write were it not for the recent invention of
glasses. He also produced a record of a sermon given in 1305, in which the
speaker, a Dominican monk named Fra Giordano da Rivalto, remarked that
glasses had been invented less than twenty years previously, and that he had
met the inventor. Based on this evidence, Redi credited another Dominican
monk, Fra Alessandro da Spina of Pisa, with the re-invention of glasses after their
original inventor kept them a secret, a claim contained in da Spina's obituary record.
While the exact date and inventor may be forever disputed, it is almost certain that
spectacles were invented between 1280 and 1300 in Italy.
These early spectacles had convex lenses that could correct both hyperopia (farsightedness), and the presbyopia that commonly develops as a symptom
of aging. Nicholas of Cusa is believed to have discovered the benefits of concave
lens in the treatment of myopia (near-sightedness). However, it was not until 1604
that Johannes Kepler published in his treatise on optics and astronomy, the first correct
explanation as to why convex and concave lenses could correct presbyopia and myopia.
Over time, the construction of spectacle frames also evolved. Early eyepieces were
designed to be either held in place by hand or by exerting pressure on the
nose. Girolamo Savonarola suggested that eyepieces could be held in place by a ribbon
passed over the wearer's head, this in turn secured by the weight of a hat. The modern
style of glasses, held by temples passing over the ears, was developed in 1727 by the
British optician Edward Scarlett.
Despite the increasing popularity of contact lenses and laser corrective eye surgery,
glasses remain very common, as their technology has improved. For
instance, it is now possible to purchase frames made of special memory
metal alloys that return to their correct shape after being bent. Other
frames have spring-loaded hinges. Either of these designs offers
dramatically better ability to withstand the stresses of daily wear and the
occasional accident. Modern frames are also often made from strong, light-weight
materials such as titanium alloys, which were not available in earlier times.
Corrective lenses are used to correct refractive errors of the eye by modifying the
effective focal length of the lens in order to alleviate the effects of conditions such as
myopia, hyperopia or astigmatism. Another common condition in older patients
is presbyopia which is caused by the eye's crystalline lens losing elasticity,
progressively reducing the ability of the lens to accommodate.
Power of lens
The power of a lens is generally measured in diopters. Glasses correcting for myopia
will have negative diopter strengths, and glasses correcting for hypermetropia will have
positive diopter strengths. Glasses correcting for astigmatism require two different
strengths placed at right angles in the same lens. Prescription lenses, made to conform
to the prescription of an ophthalmologist or optometrist, are used to make prescription
glasses, which are then verified correct using a professional lensmeter.
2. Optic Microscope
Another simple yet important invention concerning physics is the optical microscope.
The optical microscope is based on the magnifying lens. The optical microscope, often
referred to as the "light microscope", is a type of microscope which uses visible
light and a system of lenses to magnify images of small samples. Optical microscopes
are the oldest and simplest of the microscopes. Digital microscopes are now available
which use a CCD camera to examine a sample, and the image is shown directly on a
computer screen without the need for optics such as eye-pieces. Other microscopic
methods which do not use visible light include scanning electron
microscopy and transmission electron microscopy.
A simple microscope is a microscope that uses only one lens for magnification, and is
the original light microscope. Van Leeuwenhoek's microscopes consisted of a small,
single converging lens mounted on a brass plate, with a screw mechanism to hold the
sample or specimen to be examined.Demonstrations by British microscopist have
images from such basic instruments. Though now considered primitive, the use of a
single, convex lens for viewing is still found in simple magnification devices, such as
the magnifying glass, and the loupe. Light microscopes are able to view specimens
in color, an important advantage when compared with electron microscopes, especially
for forensic analysis, where blood traces may be important, for example.
Components
All optical microscopes share the same basic components:
The eyepiece - A cylinder containing two or more lenses to bring the image
to focus for the eye. The eyepiece is inserted into the top end of the body
tube. Eyepieces are interchangeable and many different eyepieces can be
inserted with different degrees of magnification. Typical magnification values for
eyepieces include 5x, 10x and 2x. In some high performance microscopes, the optical
configuration of the objective lens and eyepiece are matched to give the best possible
optical performance. This occurs most commonly with apochromatic objectives.
The objective lens - a cylinder containing one or more lenses, typically made of glass, to
collect light from the sample. At the lower end of the microscope tube one or more
objective lenses are screwed into a circular nose piece which may be rotated to select
the required objective lens. Typical magnification values of objective lenses are 4x, 5x,
10x, 20x, 40x, 50x and 100x. Some high performance objective lenses may require
matched eyepieces to deliver the best optical performance.
The stage - a platform below the objective which supports the specimen being viewed.
In the center of the stage is a hole through which light passes to illuminate the specimen.
The stage usually has arms to hold slides (rectangular glass plates with typical
dimensions of 25 mm by 75 mm, on which the specimen is mounted).
The illumination source - below the stage, light is provided and controlled in a variety of
ways. At its simplest, daylight is directed via a mirror. Most microscopes, however, have
their own controllable light source that is focused through an optical device called
a condenser, with diaphragms and filters available to manage the quality and intensity
of the light.
The objective lens is, at its simplest, a very high powered magnifying glass i.e. a lens
with a very short focal length. This is brought very close to the specimen being
examined so that the light from the specimen comes to a focus about 160 mm inside the
microscope tube. This creates an enlarged image of the subject. This image is inverted
and can be seen by removing the eyepiece and placing a piece of tracing paper over
the end of the tube. By carefully focusing a brightly lit specimen, a highly enlarged
image can be seen. It is this real image that is viewed by the eyepiece lens that
provides further enlargement.
In most microscopes, the eyepiece is a compound lens, with one component lens near
the front and one near the back of the eyepiece tube. This forms an air-separated
couplet. In many designs, the virtual image comes to a focus between the two lenses of
the eyepiece, the first lens bringing the real image to a focus and the second lens
enabling the eye to focus on the virtual image.
The whole of the optical assembly is attached to a rigid arm w hich in
turn is attached to a robust U shaped foot to provide the necessary
rigidity. The arm is usually able to pivot on its joint with the foot to allow
the viewing angle to be adjusted. Mounted on the arm are controls for
focusing, typically a large knurled wheel to adjust coarse focus, together
with a smaller knurled wheel to control fine focus.
Updated microscopes may have many more features, including reflected light (incident)
illumination, fluorescence microscopy, phase contrast microscopy and differential
interference contrast microscopy, spectroscopy, automation, and digital imaging.
Magnification
On a typical compound optical microscope, there are three objective lenses: a scanning
lens (4×), low power lens (10×)and high power lens (ranging from 20 to 100×). Some
microscopes have a fourth objective lens, called an oil immersion lens. To use this lens,
a drop of immersion oil is placed on top of the cover slip, and the lens is very carefully
lowered until the front objective element is immersed in the oil film. Such immersion
lenses are designed so that the refractive index of the oil and of the cover slip are
closely matched so that the light is transmitted from the specimen to the outer face of
the objective lens with minimal refraction. An oil immersion lens usually has a
magnification of 50 to 100×. The actual power or magnification of an optical microscope
is the product of the powers of the ocular (eyepiece), usually about 10×, and the
objective lens being used.
How it works
The essential principle of the microscope is that an objective lens with very
short focal length (often a few mm) is used to form a highly magnified real
image of the object. Here, the quantity of interest is linear magnification,
and this number is generally inscribed on the objective lens casing. In
practice, today, this magnification is carried out by means of two lenses: the objective
lens which creates an image at infinity, and a second weak tube lens which then forms
a real image in its focal plane.
Usage
Optical microscopy is used extensively in microelectronics, nanophysics, biotechnology,
pharmaceutic research and microbiology.
Optical microscopy is used for medical diagnosis, the field being
termed histopathology when dealing with tissues, or in smear tests on free cells or
tissue fragments.
3. Telescope
A telescope is an instrument designed for the observation of remote objects by the
collection of electromagnetic radiation. The first known practically functioning telescopes
were invented in the Netherlands at the beginning of the 17th century. "Telescopes" can
refer to a whole range of instruments operating in most regions of the electromagnetic
spectrum. The largest reflecting telescopes currently have objectives larger then 10 m
(33 feet).
The word "telescope" was coined in 1611 by the Greek mathematician Giovanni
Demisiani for one of Galileo Galilei's instruments presented at a banquet at
the Accademia dei Lincei.
History of the telescope
The earliest evidence of working telescopes were the refracting
telescopes that appeared in the Netherlands in 1608. Their development is credited to
three individuals: Hans Lippershey and Zacharias Janssen, who were spectacle makers
in Middelburg, and Jacob Metius of Alkmaar. Galileo greatly improved upon these
designs the following year.
The idea that a mirror could be used as an objective instead of a lens was being
investigated soon after the invention of the refracting telescope. The potential
advantages of using parabolic mirrors, primarily reduction of spherical aberration with
no chromatic aberration, led to many proposed designs and several attempts to
build reflecting telescopes. In 1668, Isaac Newton built the first practical reflecting
telescope, which bears his name, the Newtonian reflector.
The 20th century also saw the development of telescopes that worked in a wide range
of wavelengths from radio to gamma-rays. The first purpose built radio telescope went
into operation in 1937. Since then, a tremendous variety of complex astronomical
instruments have been developed.
Optical telescopes
An optical telescope gathers and focuses light mainly from
the visible part of the electromagnetic spectrum (although
some work in the infrared and ultraviolet). Optical
telescopes increase the apparent angular size of distant
objects as well as their apparentbrightness.
In order for the image to be observed, photographed,
studied, and sent to a computer, telescopes work by employing one or more curved
optical elements—usua lly made from glass—lenses, or mirrors to gather light and other
electromagnetic radiation to bring that light or radiation to a focal point. Optical
telescopes are used for astronomy and in many non-astronomical instruments,
including: theodolites (including transits), spotting
scopes, monoculars, binoculars, camera lenses, and spyglasses. There are three main
types:

The refracting telescope which uses lenses to form an image.

The reflecting telescope which uses an arrangement of mirrors to
form an image.

The catadioptric telescope which uses mirrors combined with
lenses to form an image.
There are also many other types of optical telescopes which include:

Infrared telescopes

Submillimetre telescopes

Ultraviolet telescopes

Fresnel Imager
4. Optical fibre
The guiding of light in media using the concept of total internal
reflection was first discussed during the 19th
century. The idea is often attributed to J. Tyndall who demonstrated the
guiding of light in a water jet at the
Royal Society in London in 1854, following a suggestion by M. Faraday.
Usage
Optical fiber can be used as a medium for telecommunication and networking because
it is flexible and can be bundled as cables. It is especially advantageous for longdistance communications, because light propagates through the fiber with little
attenuation compared to electrical cables. This allows long distances to be spanned
with few repeaters. Additionally, the per-channel light signals propagating in the fiber
have been modulated at rates as high as 111 gigabits per second by NTT, although 10
or 40 Gb/s is typical in deployed systems. Each
fiber can carry many independent channels,
each using a different wavelength of light
(wavelength-division multiplexing (WDM)). The
net data rate (data rate without overhead bytes)
per fiber is the per-channel data rate reduced
by the FEC overhead, multiplied by the number
of channels (usually up to eighty in
commercialdense WDM systems as of 2008).
The current laboratory fiber optic data rate record, held by Bell Labs in Villarceaux,
France, is multiplexing 155 channels, each carrying 100 Gb/s over a 7000 km fiber.
For short distance applications, such as creating a network within an office building,
fiber-optic cabling can be used to save space in cable ducts. This is because a single
fiber can often carry much more data than many electrical cables, such as 4 pair Cat5 Ethernet cabling.Fiber is also immune to electrical interference; there is no cross-talk
between signals in different cables and no pickup of environmental noise. Non-armored
fiber cables do not conduct electricity, which makes fiber a good solution for protecting
communications equipment located in high voltage environments such as power
generation facilities, or metal communication structures prone to lightning strikes. They
can also be used in environments where explosive fumes are present, without danger of
ignition. Wiretapping is more difficult compared to electrical connections, and there are
concentric dual core fibers that are said to be tap-proof.
Although fibers can be made out of transparent plastic, glass, or a combination of the
two, the fibers used in long-distance telecommunications applications are always glass,
because of the lower optical attenuation. Both multi-mode and single-mode fibers are
used in communications, with multi-mode fiber used mostly for short distances, up to
550 m (600 yards), and single-mode fiber used for longer distance links. Because of the
tighter tolerances required to couple light into and between single-mode fibers (core
diameter about 10 micrometers), single-mode transmitters, receivers, amplifiers and
other components are generally more expensive than multi-mode components.
Fiber optic sensors
Fibers have many uses in remote sensing. In some applications, the sensor is itself an
optical fiber. In other cases, fiber is used to connect a non-fiberoptic sensor to a
measurement system. Depending on the application, fiber may be used because of its
small size, or the fact that no electrical power is needed at the remote location, or
because many sensors can be multiplexed along the length of a fiber by using different
wavelengths of light for each sensor, or by sensing the time delay as light passes along
the fiber through each sensor. Time delay can be determined using a device such as
an optical time-domain reflectometer.
Optical fibers can be used as sensors to measure strain, temperature, pressure and
other quantities by modifying a fiber so that the quantity to be measured modulates
the intensity, phase, polarization, wavelength or transit time of light in the fiber. Sensors
that vary the intensity of light are the simplest, since only a simple source and detector
are required. A particularly useful feature of such fiber optic sensors is that they can, if
required, provide distributed sensing over distances of up to one meter.
Extrinsic fiber optic sensors use an optical fiber cable, normally a multi-mode one, to
transmit modulated light from either a non-fiber optical sensor, or an electronic sensor
connected to an optical transmitter. A major benefit of extrinsic sensors is their ability to
reach places which are otherwise inaccessible. An example is the
measurement of temperature inside aircraft jet engines by using a fiber
to transmit radiation into a radiation pyrometer located outside the
engine. Extrinsic sensors can also be used in the same way to measure the internal
temperature of electrical transformers, where the extreme electromagnetic
fields present make other measurement techniques impossible. Extrinsic sensors are
used to measure vibration, rotation, displacement, velocity, acceleration, torque, and
twisting.
5. Fabrications of refractive blazed holograms
Methods and apparatus for fabricating refractive blazed holograms having high single
image diffraction efficiencies. A reflective blazed hologram made with a single
wavelength light source may be modified for high blazed efficiencies at any desired
wavelength. A reflective blazed hologram surface is replicated onto the surface of a
material of higher refractive index, with a shorter wavelength of light utilized fore
reconstruction. A further embodiment is to replicate a reflective blazed hologram onto
the surface of a material that can be made to undergo an isotropic dimension increase
or decrease. When the desired dimension change has taken place,
the blazed surface thereof would again be replicated onto the surface
of a suitable transparent material of the proper refractive index. Thus,
refractive blazed holograms blazed for any wavelength can be obtained
Brief Summary Of The Invention
In accomplishing the above and other desired aspects of the present invention,
Applicant has invented improved apparatus and methods for blazed holographic
information recording. In a first embodiment, a reflective blazed hologram of one
constructing blaze wavelength is replicated onto the surface of a material having a
different refractive index to form a refractive blazed hologram having a different blaze
wavelength. A second embodiment replicates a reflective blazed hologram onto the
surface of a material
that can be made to undergo an
isotropic dimension change. Depending upon the material
to be used, a refractive blazed hologram blazed for any
wavelength can be obtained. A third embodiment of the invention illustrates the
replication of a reflective hologram onto a material which is isotropically expanded or
shrunk, the ratio of the second wavelength to the first wavelength being the factor of
multiplication thereof.
Detailed Description Of The Invention
As hereinabove set forth, Yu N. Denisyuk introduced the concept of a hologram
produced by exposing a thick photographic emulsion to a standing optical wavefield.
The standing wavefield was created by allowing light reflected from an object to
interfere with a reference beam propagating in the opposite direction. The photographic
emulsion recorded the antinodal surfaces of the wavefield as silver deposits in the
emulsion volume. These silver deposits served as reflection surfaces for the
reconstruction of the object wavefield.
It may be expected that boundary conditions equivalent to a single isolated standing
wave surface can be obtained by isolating the fragments of standing wave surfaces
located in the volume of space between two parallel planes spaced approximately onehalf wavelength apart. Such a hologram is in effect blazed, and like a blazed diffraction
grating, reflects a maximum amount of light into a single diffraction order. Its groove
shape follows sections of the standing wave surfaces。
Light transmitted through an uncoated, as opposed to one coated with aluminum, for
example, blazed hologram can be made to undergo a phase change of one wavelength
between adjacent blaze surfaces. When this is done, light contributions from all blazed
surface segments will add in phase to produce an image, and thus is produced a
refractive blaze hologram.
For maximum efficiency in a reflective blazed hologram it is advantageous to have the
angle of diffraction coincident with the angle of reflection from the facets on the blazed
surface. However, in a refractive instance for a given wavelength, when the reflective
situation is optimum, the phase change is considerably distorted, causing among other
things the transmitted light energy to be divided rather symmetrically among numerous
images.
Images from reflective blazed holograms can be reconstructed by reflecting light either
from the air side or from the substrate side of the blazed surface. Because the
wavelength is longer in air than in the substrate the hologram will be blazed for different
wavelengths in the two cases. For purposes of illustrating the principles of this invention
in the simplest manner the equation shown above and all subsequent equations
assume the image is being reconstructed by reflecting light from the air side of the
blazed surface, where the refractive index is 1.
In the foregoing there has been disclosed methods and apparatus for effectively utilizing
holographic principles in the construction of blazed holograms for refraction and for
unavailable light source wavelengths. The use of transmission blazed holograms greatly
enhances their potential application as optical imaging elements over the reflective
blazed holograms as set forth above in the copending application. While the invention
has been described with reference to specific embodiments, it will be understood by
those skilled in the art that various changes may be made and equivalents may be
substituted for elements thereof without departing from the true spirit and scope of the
invention. In addition, many modifications may be made to adapt to a particular situation
without departing from the essential teachings of the invention.
References:
http://www.ehow.com/how-does_4564464_glasses-work.html
http://ezinearticles.com/?How-Do-Glasses-Work?&id=1491197
http://www.howstuffworks.com/lens.htm
http://kidshealth.org/kid/feel_better/things/glasses.html
http://vision.about.com/od/eyeglasses/f/Pinhole_Glasses.htm
http://www.answers.com/topic/optical-microscope
http://opticalmicroscope.com/
http://www.sv.vt.edu/classes/MSE2094_NoteBook/96ClassProj/experimental/optical.html
http://micro.magnet.fsu.edu/primer/pdfs/microscopy.pdf
http://www.olympusmicro.com/
http://science.howstuffworks.com/telescope.htm
http://www.quadibloc.com/science/opt01.htm
http://www.yesmag.ca/how_work/telescope.html
http://www.howdotelescopeswork.com/
http://www.howstuffworks.com/fiber-optic.htm
http://www.wisegeek.com/what-is-optical-fiber.htm
http://www.freepatentsonline.com/3623798.html
http://www.patentstorm.us/patents/7271957/claims.html