Microscopes Flashcards
What are the advantages of light microscopes?
Can observe living cells so it is possible to watch processes as they occur
-Relatively cheap
Portable - field and lab use
Easy to use
What are the disadvantages of light microscopes?
Limited resolution
Why is a compound light microscope better than a simple light microscope?
The objective /eyepiece sense configuration allows for much higher magnification and reduced chromatic aberration
How does a light microscope work?
Visible light passes through the specimen and is bent through the lens system, allowing the user to see a magnified image. Objective sense produces a magnified image and the image is magnified by eyepiece sense.
How does a TEM microscope work?
Sample is cut into extremely thin slices before imaging
Electron beam passes trough slice ( rather than scanning over its surface) to produce a 2D image
What are the advantages of a TEM microscope?
Best resolution
Able to view internal features
Able to look at relationships between structures
Lets you look at a very thin cross section of an object
What are the disadvantages of a TEM microscope?
Very expensive and can only be used inside a carefully controlled environment in a dedicated space
Cant be used to look at living specimens
Specimen has to be viewed in a vacuum so sample can’t have any moisture in it
Specimen can be damaged in preparation processes
How does a SEM microscope work?
Beam of electron moves back and forth across the surface of cells or tissue and reflected electrons are collected to form a 3D image of the surface
What are the advantages of a SEM microscope?
3D image of surface
What are the disadvantages of a SEM microscope?
Very expensive and can only be used inside a carefully controlled environment in a dedicated space
Cant be used to look at living specimens
Specimen has to be viewed in a vacuum so sample can’t have any moisture in it
Specimen can be damaged in preparation processes
Resolution is a limitation
What are artefacts?
Structures that are produced due to preparation process
Why are electron microscopes better to use than light microscopes of detail?
Electron microscopes produce an image using a beam of electrons. Electrons have much shorter wavelength than visible light , this allows for production of higher -resolution images.
What are electron microscopes use to examine?
Whole cells but also sub cellular structures + compartments within them.
What is a limitation of electron microscopes?
Samples must be placed under a vacuum to ensure the electron beams travel in a straight line; electrons are very small and easily scattered by particles in the air.
Specimen can be damaged by electron beam and there is a problem with artefacts.
What are the advantages of a laser scanning confocal microscope?
Able to look at living cells
Highlights individual components of the cell
Better understanding of relationship between cells
A 3D image can be produced by creating images at different focal points
