specimens are visualized because of the slight differences in contrast (density) that exist between them and their surrounding medium. 

2 sets of lenses form the image: objective lens and ocular lens.

Light source is focused on the specimen by a 3rd lens: the condenser. 

Total magnification = objective magnification x ocular magnification

maximum magnification is 1,500X

the ability to distinguish two adjacent objects as separate and distinct.

determined by the wavelength of light used.

limit of resolution for light icroscope is about 0.2µm. 

improves contrast for bright-field microscopy

stains can be

• differential: creates noticeable differences
• non-differential:no noticeable difference

Ex of common stains: methylene blue, safranin, crystal violet

• improve contrast without the use of stain
• allows the observation of wet-mount (living) preparations

-Frits Zernike

phase ring in objective lens amplifies differences in refractive index (factor by which light is slowed as it passes through a material) of the cell from their surroundings

light reaches the specimen from the sides only

only light reaching the lens is scattered by the specimen -- the specimen appears light on a dark background.

• good for observing motility of microorganisims i.e. flagella
• better resolution than light microscopy, bright-field and phase-contrast microscopes