Microscopy (1.1.5) PDF

Microscopy (1.1.5) Extremely small structures such as cells cannot be seen without microscopes, which enlarge the image. The first cells of a cork were observed by Robert Hooke in 1665 using a light microscope. It has two lenses, an...

Microscopy (1.1.5) Extremely small structures such as cells cannot be seen without microscopes, which enlarge the image. The first cells of a cork were observed by Robert Hooke in 1665 using a light microscope. It has two lenses, an objective and eyepiece The objective lense produces a magnified image, which is then magnified and directed into the eye by the eyepiece lense It is usually illuminated from underneath They have, approximately, a maximum magnification of x2000 and a resolving power (this affects resolution: the ability to distinguish between two points) of 200nm (the lower the RP, the more detail is seen) Used to view tissues, cells and large sub-cellular structures In the 1930s the electron microscope was developed, enabling scientists to view deep inside sub-cellular structures, such as mitochondria, ribosomes, chloroplasts and plasmids. Electrons, as opposed to light, are used to form an image because the electrons have a much smaller wavelength than that of light waves There are two types: a scanning electron microscope that create 3D images (at a Untitled 1  slightly lower magnification) and a transmission electron microscope which creates 2D images detailing organelles They have a magnification of up to x2,000,000 and resolving power of 10nm (SEM) and 0.2nm (TEM) Common calculations: 1. Magnification of a light microscope: magnification of the eyepiece lens x magnification of the objective lens 2. Size of an object: size of image/magnification = size of object (this formula can be rearranged to obtain the other values, make sure you are in the same units!) Untitled 2