Optical microscope

•Optical microscopes are compound microscopes▫Occular lens▫Optical lens

•Light passes through the specimen.

•Different areas absorb different amounts (and wavelengths) of light.

•Dark areas that absorb a lot of light are called optically dense regions.

Optical microscope•The lenses refract light and so cause the

image to appear larger.•The resolution is limited to the

wavelength of light.•Objects smaller than 0.2µm can not be

resolved, and so seen, by a light microscope.

NB. Take care with language- do not talk about the wavelength of the microscope but the wavelength of light!

Definitions•Magnification- making an object appear

larger than it is.•Resolution- ability of an instrument to

distinguish between 2 points that are close together. Allows for more detail.

•Micrometre- µm 1/1000 mm or 1/1000000 m