2.1 Microscopy Flashcards
What is resolution?
The smallest separation at which two separate objects/points can be distinguished
What is the resolution of a microscope limited by?
The wavelength of light used
How does a light microscope work?
- uses a series of lenses to produce an image that can be viewed directly at the eyepiece
- light passes from a bulb under the stage, through a condenser lense and then through the specimen.
- this beam of light is passed through an objective and then eyepiece lense
Do light microscopes have high or low resolution?
Low
What is the maximum resolution of s light microscope?
200nm
What is the maximum magnification of a light microscope?
x1500
What are the advantages of light microscopes?
- cheap
- portable
- you can stain the sample
- able to study living material
What are the disadvantages of light microscopes?
- low resolution
- small cell organelle are not visible
What is the staining technique?
Coloured stains bind to chemicals on or in the specimen allowing the specimen to be seen, due to increased contrast
What is magnification?
How much bigger the image is compared to the original object
What is sectioning?
- Specimens are embedded in wax
- thin sections are cut out without distorting the specimen
What is sectioning useful for?
Making slides/sections of soft tissues such as brain
What are laser scanning microscopes also called?
Confocal microscopes
How do laser scanning microscopes work?
- use a laser to scan an object point by point
- can be used to view slices in the specimen without damaging it
- slices can be reformed into a 3D image
What are advantages of laser scanning microscopes?
- high resolution and contrast
- can observe whole organisms and individual cells
- observe living and fixed specimens
- can focus structures at different depths of the specimen
What are some disadvantages of laser scanning microscopes?
- lower resolution than electron microscope
- time consuming (sample is scanned point to point)
How do you identify a laser scanning microscope image?
- fluorescence
- black background
- multiple layers
What is a TEM?
Transmission electron microscope
How does a TEM work?
Transmit a beam of electrons through a thin specimen and then focus the electrons to form an onscreen image
What are the advantages of TEMs?
- highly detailed images of cells and organelles
- high resolution
What are some disadvantages or TEMs?
- can’t study living material due to extensive preparation and vacuum
- expensive
- specific skill and training for sample preparation
What is the maximum resolution of a TEM?
0.1 nm
What is the maximum magnification of a TEM?
x500000
What is a SEM?
Scanning electron microscope
How does an SEM work?
By scanning a fine beam of electrons onto a specimen and collecting the electrons scattered by the surface
What are advantages of SEMs?
- 3D images of cell surface
- detailed
- powerful magnification
What are some disadvantages of SEMs?
- can’t see inside cells
- expensive
- can’t study living organisms
- specific training for sample preparation
What is the maximum magnification of an SEM?
x100000
What is the maximum resolution of an SEM?
2nm
What is the formula for calculating magnification?
Magnification= image size ➗ actual size
What stain (chemical ) is used for staining plant cells?
Iodine
What stain is commonly used for staining animal cells?
Methylene blue
