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IFFAT FATIMA. UOG. ELECTRON MICROSCOPE. Contents. History LM Vs EM Electron microscope Principle Types of EM Application & importance. History of Microscope. 1590-tube microscope by dutch glass maker. 1665-Robert hooke’s microscope. Continued…………………………….

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Contents
Contents

  • History

  • LM Vs EM

  • Electron microscope

  • Principle

  • Types of EM

  • Application & importance


History of microscope
History of Microscope

1590-tube microscope by dutch glass maker

1665-Robert hooke’s microscope


Continued
Continued……………………………

1674-Antonee van leeuwenhooke

TEM co-invented by Ernst Ruska (1931)





Comparison
Comparison

Light microscope

Electron microscope

Resolution: 0.2nm

Magnification: 2‚000‚000x

Illumination: Electron

Electromagnetic lenses

Objects seen: orgenelles‚ proteins‚ viruses‚ small molecules etc.

Dead specimen

Higher resolving power

Focus: vaccum & magnetic lense

Resolution: 0.2μm to 200nm

Magnification: 2000x

Illumination: Light

Glass lenses

Objects seen: frog's egg cells‚ cell wall‚ cilia‚ flagella‚ nucleus & other organelles etc.

Living specimen

Lower resolving power

Focus: condenser lense


Electron microscope1
Electron microscope

  • Electron microscope is a scientific instrument that uses a beam of energetic electrons to examine objects on a very fine scale.

    Why electron beam?

  • Wave nature of particles



Transmission electron microscope
Transmission electron microscope

Instrumentation

  • Electron Source

  • Electromagnetic lense system

  • Sample holder

  • Imaging system


Working
Working

  • Emission of a high voltage beam of electrons.

  • Focusing of beam on specimen.

  • Transmission through the specimen.

  • Magnification of the image.

  • Recording of the image by fluorescent screen, light sensitive sensor (camera).



Sample preparation
Sample preparation

  • Fixation

  • Rinsing

  • Post fixation

  • Dehydration

  • Infiltration

  • Polymerization

  • Sectioning


Applications
Applications

  • Ultra-structure analysis

  • Crystal structure


Scanning electron microscope
Scanning Electron microscope

  • Emission of a beam of by an electron gun.

  • Passage of electron beam through the vacuum.

  • Focusing of beam down toward the sample.

  • Ejection of X-rays & es. From sample after hitting.

  • Collection of by detectors & conversion to a signal.

  • Transmission of signal to a screen/ final image



Sample preparation1
Sample preparation

  • Metals require no preparation

  • Non metals require coating of a thin layer of conductive material.


Applications1
Applications

  • Medical & physical science

  • Semiconductor industry

  • Examination of a large specimen range.



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