Physics Inventionsx - 2010SMTPSec3

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20 Φεβ 2013 (πριν από 4 χρόνια και 8 μήνες)

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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

䝬asses

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. So
me
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 meni
scal

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 l
etters, however
small and indistinct, are seen enlarged and more clearly through a glo
be or glass filled
with water
.



Around 12
84 in Italy,

Salvino D'Armate

is credited with inventing the first wearable eye
glasses.

The earlies
t 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

ser
mon

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 h
e 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.

Th
ese early spectacles had

convex lenses

that could correct both

hyperopia

(far
-
sightedness), and the

presbyopia

that commonly develop
s 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

as
tronomy
, 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 pr
essure 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 exa
mine 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 len
s

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 pri
mitive, 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 hig
h 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

apochroma
tic

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.

Th
e 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 si
mplest, 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
mic
roscope 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
ima
ge 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 le
ns 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
t
he 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.


Magnific
ation

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 im
mersion 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 microb
iology.


Optical microscopy is used for

medical diagnosis
, the field being
termed

histopa
thology

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
th
e

Accademia dei Lincei
.


History of the telescope

The earliest e
vidence of working telescopes were the

refracting
telescopes

that appeared in the

Netherla
nds

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 c
omplex 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 apparent
brightness
.


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

u
sua

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,
includin
g:

theodolites

(including

transits
),

spotting
scopes
,

monoculars
,

binoculars
,

camera lenses
, a
nd

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 tele
scopes



Fresnel Imager













4.
Optical fibre


The guiding of light in media using the

concept of total internal
reflection was first

discussed during the 19th


cent
ury
.
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 long
-
distance communications, because light propagates through the fiber with l
ittle
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 differen
t wavelength of light
(
wavelength
-
division multiplexing

(WDM)). The
net data rate (data rate without overhead bytes)
per fiber is the per
-
ch
annel data rate reduced
by the FEC overhead, multiplied by the number
of channels (usually up to eighty in
commercial
dense WDM

systems as of 2008).
The current laboratory fiber optic dat
a 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 s
ave space in cable ducts. This is because a single
fiber can often carry much more data than many electrical cables, such as 4 pair

Cat
-
5

Ethernet cabling.Fiber is also immune to electrical inte
rference; 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 communication
s, 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 t
hat no

electrical power

is needed at the remote location, or
because many sensors can be

multipl
exed

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 sim
ple 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. Extrin
sic 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


materi
al 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 increas
e


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.
T
hus,


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


wa
velength 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 one
-


half 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 o
f 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


refractiv
e 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 c
onstruction 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


subst
ituted 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