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TELESCOPES

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ContentsContents
What is telescope?What is telescope?
How it is named?How it is named?
Types of Telescopes?Types of Telescopes?
How different types of telescopes work?How different types of telescopes work?

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TelescopeTelescope
Designed for theDesigned for the

observation ofobservation of remote objectsremote objects

to magnify distant objectsto magnify distant objects

to make faraway objects appear much closerto make faraway objects appear much closer
Name Telescope came from Greek:Name Telescope came from Greek:

teletele = 'far' and= 'far' and skopeinskopein = 'to look or see';= 'to look or see';

teleskoposteleskopos = 'far-seeing‘.= 'far-seeing‘.
Telescopes are mainly of two types:Telescopes are mainly of two types:

Reflecting TelescopeReflecting Telescope

Refracting MicroscopeRefracting Microscope

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Reflecting TelescopeReflecting Telescope
A telescope in which lightA telescope in which light
from the object is initiallyfrom the object is initially
focused by a concave mirrorfocused by a concave mirror

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Refracting TelescopeRefracting Telescope
A telescope in which a lensA telescope in which a lens
receives and focuses lightreceives and focuses light
that is then viewed through athat is then viewed through a
second, magnifying lens insecond, magnifying lens in
the eyepiecethe eyepiece..

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MICROSCOPES

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ContentsContents
 What is Microscope?What is Microscope?
 How it is namedHow it is named
 Types of Microscopes?Types of Microscopes?
 How Different types of Microscopes work?How Different types of Microscopes work?

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MicroscopeMicroscope
Designed forDesigned for

viewing objects that are too small to be seen by the naked eyeviewing objects that are too small to be seen by the naked eye
Microscope name came from Greek:Microscope name came from Greek:

((micronmicron) = small + () = small + (skopeinskopein) = to look at) = to look at
Main types of Microscopes:Main types of Microscopes:

Optical MicroscopeOptical Microscope
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Electron MicropscopeElectron Micropscope
Transmission Electron MicroscopeTransmission Electron Microscope
Scanning Electron MicroscopeScanning Electron Microscope

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Optical microscopesOptical microscopes
UseUse visible wavelengthsvisible wavelengths of lightof light
The simplest and hence most widely used type in biology and geologyThe simplest and hence most widely used type in biology and geology
Optical microscopes use refractive lenses to focus light into the eye or anotherOptical microscopes use refractive lenses to focus light into the eye or another
light detectorlight detector

typically of glass and occasionally of plastictypically of glass and occasionally of plastic
Typical magnification of a light microscope is up to 1500x with a theoreticalTypical magnification of a light microscope is up to 1500x with a theoretical
resolution of around 0.2 micrometres.resolution of around 0.2 micrometres.
Various wavelengths of light are sometimes used for special purposesVarious wavelengths of light are sometimes used for special purposes

UltravioletUltraviolet light is used to illuminate the object being viewed in order tolight is used to illuminate the object being viewed in order to
excite a fluorescent dye which then emits visible light.excite a fluorescent dye which then emits visible light.

InfraredInfrared light is used to study thick slices of biological tissue becauselight is used to study thick slices of biological tissue because
infrared light's permits viewing deeper into tissue.infrared light's permits viewing deeper into tissue.
x-ray microscopex-ray microscope

Uses electromagnetic wavelengthsUses electromagnetic wavelengths not visiblenot visible to the human eye are oftento the human eye are often
called optical microscopes.called optical microscopes.

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Optical MicroscopeOptical Microscope
A device that uses a lens orA device that uses a lens or
system of lenses to produce asystem of lenses to produce a
greatly magnified image of angreatly magnified image of an
object. An opticalobject. An optical
microscope uses transmittedmicroscope uses transmitted
or reflected light to obtainor reflected light to obtain
the image.the image.

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How do Electron MicroscopesHow do Electron Microscopes
Work?Work?
Electron Microscopes (EMs) function exactly as their opticalElectron Microscopes (EMs) function exactly as their optical
counterpartscounterparts
EMs use a focused beam of electrons instead of light to "image" theEMs use a focused beam of electrons instead of light to "image" the
specimen and gain information as to its structure and composition.specimen and gain information as to its structure and composition.
A vacuum is necessary for its proper function as electrons are minuteA vacuum is necessary for its proper function as electrons are minute
particles that can be deflected even by air particles.particles that can be deflected even by air particles.
The basic steps involved in all EMs:The basic steps involved in all EMs:

A stream of electrons is formed by the Electron Source andA stream of electrons is formed by the Electron Source and
accelerated toward the specimen using a positive electrical potentialaccelerated toward the specimen using a positive electrical potential
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This stream is confined and focused using metal apertures andThis stream is confined and focused using metal apertures and
magnetic lenses into a thin, focused, monochromatic beam.magnetic lenses into a thin, focused, monochromatic beam.

This beam is focused onto the sample using a magnetic lensThis beam is focused onto the sample using a magnetic lens
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Interactions occur inside the irradiated sample, affecting theInteractions occur inside the irradiated sample, affecting the
electron beamelectron beam

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Transmission Electron MicroscopeTransmission Electron Microscope
A high-poweredA high-powered
microscope that usesmicroscope that uses
beams of electronsbeams of electrons
focused by an electronfocused by an electron
lens to create a magnifiedlens to create a magnified
image on a fluorescentimage on a fluorescent
screen or photographicscreen or photographic
plateplate..

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Scanning Electron MicroscopeScanning Electron Microscope
It is a microscope that uses aIt is a microscope that uses a
beam of electrons to scan anbeam of electrons to scan an
object and produce anobject and produce an
enlarged image of it on aenlarged image of it on a
cathode-ray.cathode-ray.

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OverviewOverview
Telescopes come in two types:Telescopes come in two types:

Refractor telescope : uses glass lensesRefractor telescope : uses glass lenses
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Reflector telescope : uses mirrors instead of the lensesReflector telescope : uses mirrors instead of the lenses
Microscopes can largely be separated into two classesMicroscopes can largely be separated into two classes

Optical theory microscopes : electromagnetic waves are usedOptical theory microscopes : electromagnetic waves are used

Electron microscopes: electron beam is usedElectron microscopes: electron beam is used

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