Microscopes and Microscopy Flashcards
What are the 3 types of microscopes?
- optical microscopes
- transmission electron microscopes
- scnning electron microscopes
How do light (optical) microscopes work?
Relies on lenses to focus a beam of light
How do transmission electron microscopes work?
- uses a beam of fast travelling electrons with a wavelength of 0.004nm fired from a cathode
- the beam of electrons passes through the specimen
- some pass through and are focused on the screen/ photographic plate
How do scanning electron microscopes work?
Electrons do NOT pass through the specimen, instead cause secondary electrons to ‘bounce off’ the specimen’s surface and be focused on the screen
Define photomicrograph
Photograph of the image seen using an optical microscope
Which type of microscope produces a photomicrograph?
An optical microscope
What are the benefits of using an optical microscope?
- linear magnification
- stains not required for coloured objects
- can be used to study whole living organisms
What is a drawback of using an optical microscope?
It has a limited resolution
Define electron micrograph
Electrons form an image that a photograph is taken of
What microscopes produce electron micrographs?
- scanning electron microscopes
- transmission electron microscopes
Describe the type of electron micrograph produced by a transmission electron microscope
- 2D
- black and white image
State the benefits of a transmission electron microscope
- high magnification achieved
- 0.1 nm resolution
- ultrastructure (internal structure) seen
State the drawbacks of a transmission electron microscope and a scanning electron microscope
hint: both have the same drawbacks
- need skill and training to use
- specimens have to be chemically fixed
- speciment must be viewed under a vacuum
- can’t study living things
Describe the type of image produced by a scanning electron microscope
- 3D
- black and white image
- a computer can artificially add colour onto the image
State the benefits of a scanning electron microscope
- whole specimen can be used
- higher magnification and resolution