2.1 Microscopy Flashcards
How does a light microscope work?
A compound light microscope has two lenses - the objective lens (which is placed near the specimen) and an eyepiece lens (through which the specimen in viewed). The objective lens produces a magnified imagine which is magnified again by the eyepiece lens.
Illumination is usually provided by a light underneath the sample.
What are the 4 ways you can prepare a sample/ specimen?
- dry mount
- wet mount
- squash slides
- smear slides
Describe how a dry mount is used to prepare a sample
- Solid specimens are viewed whole (e.g. hair, pollen, dust) or cut into thin slices with a sharpe blade, this is called sectioning (e.g. plants or muscle tissue)
- The specimen is placed on the centre of the side and a cover slip is placed over the sample
Describe how a wet mount is used to prepare a sample
- specimens are suspended in a liquid such as water or an immersion oil
- a cover slip is placed from an angle
E.g. aquatic samples (to observe their movement) nd other living organisms can be viewed this way
Describe how to use squash slides to prepare specimen samples
- a wet mount is first prepared, then a lens tissue is used to gently press down the cover slip
- using squash slides is a good technique for soft samples to look at a thin layer
- care needs to be taken that the cover slip is not broken when being pressed
E..g. Root tip squashes are used to look at cell division
Describe how smear slides are used to prepare specimen samples
- The edge of a slide is used to smear the sample, creating a thin, even coating on another slide
- a cover slip is then placed over the sample
E.g. a sample of blood could be prepared using a smear slide. This is a good way to view the cells in the blood
What is differential staining?
Staining that can distinguish between two types of organisms that would otherwise be hard to identify
