Microscopes

-the number of times larger an image appears compared with the size of the object

-how detailed the image is, the ability of a microscope to distinguish between two points that are close together

-Magnification= image size/actual size

-Magnification x actual size

-Image size/magnification

-Electron and Light microscope

-Uses visible light-> part of the electormagnetic spectrum that has a wavelength of 400-700nm Magnification=x1500 Resolution=0.2 (200nm)

• Pro: • Relatively cheap • Observe living things • No training needed • Easy to use

Con: • Limited magnification • Limited resolution • Can not see internal structures • No 3D images

• TEM (Transmission electron microscope) - SEM(Scanning electron microscope)

• Uses electromagnets to focus a beam of electrons which produces 2D image • Denser part absorb more electrons so becomes darker on the image

• High resolution-> see small organelles like ribosomes • Can look at internal structures • Image is 2D • Angles can affect how they appear

• Magnification=More than 1,000,000x - Resolution=0.0002 micrometer

• Specimen coated with fine metal • Beam of electrons across specimen. Which knocks off electrons to form image • Produced on computer

• Image is black and white-false colour can be added by programmes • Shows the surface of the specimen not the internal structures • Image is 3D • Lower resolution that TEM

• Resolution=0.002 - Magnification=x500,000

-Laser scanning confocal microscope

• Use laser beams to scan specimen that are tagged with fluorescent dye • Laser beam is aimed at the beam splitter • Splits the beam+some light directed at specimen • Laser hits dye which gives off fluorescent dye • Detector generates an image

Sample preparation: • Dry mount • Wet mount • Squash slides • Smear slides

• Solid specimen are viewed whole or cut into very thin slices with a sharp knife (called sectioning) • Specimen is placed in centre of slide and cover slip placed over the sample • Examples; hair, pollen, dust

• Specimens are suspended in a liquid such as water or immersion oil • Cover slip placed on from an angle • Examples; aquatic samples

• Wet mount prepared first, then a lens tissue is used to gently press down the cover slip • Good technique for soft samples

• Edge of a slide is used to smear the sample-> creating a thin coating another slide • Cover slip is placed over the sample

• Are attracted to negatively charged materials in cytoplasm leading to staining of cell components • Crystal Violet and Methylene blue