write short notes on ordinary light microscope,light microscope,electron microscope. .?

Answer 1

A normal light microscope uses glass lenses and is good up to about 500 x magnification. Above this magnification, light microscopes can be used if a drop of low refractive index oil is put between the objective lens and the subject being viewed. This will let you see objects up to just over 1000 x magnification. Above this the wavelength of normal visible light (approx 400 to 700 nm) limits the resolution of the image.
Scanning electron microscopes (SEM) have much higher resolution due to the very short wavelength of electrons. They can magnify up to 500,000 x. They operate by scanning a beam of electrons across the subject in a raster fashion. The electrons interact and reflect from the surface of the subject giving an electrical signal at the detector. The signal varies depending on the exact nature of the surface. The signal received by the detector is scanned across a TV screen giving an image of the object at high magnification. If the electron beam scans an area 10 microns x 10 microns and the electrical signal is displayed on a screen 10 cm x 10 cm, then the magnification will be 10,000 x.

Only one small problem! The surface of the subject being viewed needs to be conductive. This can be achieved on non-conductive surfaces by evaporating a few Angstoms of aluminium or gold.

Answer 2

Basically this is what they mainly ask in exams-

optic microscope (ordinary microscope)
uses long wavelengths, and a lens with a magnifier in, so you can see objects but not as well as an electron microscope as an electron microscope has a smaller wavelength, which creates a higher resolution(the ability to distinguish between two close objects)

there's also 2 types of electron microscope, transmission and scanning. we did this in September so its good revision for me :)

a transmission microscope uses a small cross section of the sample, so it has to be dead, that's a downside to it. It sends beams of electrons to the sample and it produces the image on a photographic plate.You are able to see the ultra cellular organelles, in a 2D image on a monitor, its very Hi tech so schools an colleges don't use it!

Scanning microscope can produce a better quality 3D picture.

hope this is some help, some revision for me :)

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Answer 4

haha...sounds like first year biology to me!

http://en.wikipedia.org/wiki/Microscopy