Microscopes

• Magnification is how much bigger an object appears compared to the original object.
• Resolution: The ability to distinguish two points that are close together.
• Optical microscopes: Cheap, easy to use, portable, magnification up to x1500 (can see the larger structures inside of cells), maximum resolution of 200nm.
• Laser scanning microscopes: Use a fluorescent dye, think section is scanned use a laser beam, multiple depths of tissue sections are scanned +thick or 3D specimens, external 3D structures, high resolution - slow process, photo damage can occur
• Electron microscope: use electrons to form an image, maximum resolution of 0.2 nm, can observe small organelles like ribosomes, x1500000, two types Transmission electron microscopes and scanning electron microscopes.
• Transmission electron microscopes: focus a beam of electrons, through the specimen, denser parts absorb more electrons so they appear darker on the image. +high resolution, can seen internal structures. - thin specimens, cannot be live specimens, not a colour image
• Scanning electron microscopes: scan a beam of electrons, bounces of the specmien and these electrons are detected. + can be used on thick or 3D images, observe external structures. - lower resolution than TEMs, cannot observe live specimens, no colour image
• differential staining is when specimens are stained with multiple dyes to ensure the different tissues within the specimens show up.
• Staining for electron microscopy: must be stained in order for the specimen to absorb electrons, the dyes will show up black or different shades of grey, heavy metal compounds are usually used a they observe electrons well.
• 1mm is 1000 micrometers , 1 micrometer is 1000 nm
• Total magnification for a light microscope is the eyepiece lens mag x objective lens mag