Question

Define scanning electron microscope and electron microscope

Answer 1

A scanning electron microscope (SEM) is a type of electron microscope that produces images of a sample by scanning the surface with a focused beam of electrons. The electrons interact with atoms in the sample, producing various signals that contain information about the sample's surface topography and composition. The electron beam is scanned in a raster scan pattern, and the beam's position is combined with the detected signal to produce an image. SEM can achieve resolution better than 1 nanometer. Specimens can be observed in high vacuum in conventional SEM, or in low vacuum or wet conditions in variable pressure or environmental SEM, and at a wide range of cryogenic or elevated temperatures with specialized instruments.[1]

The most common SEM mode is detection of secondary electrons emitted by atoms excited by the electron beam. The number of secondary electrons that can be detected depends, among other things, on specimen topography. By scanning the sample and collecting the secondary electrons that are emitted using a special detector, an image displaying the topography of the surface is created.

Answer 2

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$\huge\mathfrak\purple{light\: microscope}$
Illuminating source is the Light.

Specimen preparation takes usually few minutes to hours.

Live or Dead specimen may be seen.

Condenser, Objective and eye piece lenses are made up of glasses.

It has low resolving power (0.25µm to 0.3µm).

It has a magnification of of 500X to 1500X.

The object is 5µm or thicker.

Image is Colored.

Vacuum is not required.

There is no need of high voltage electricity.

There is no cooling system.

$\huge\mathfrak\purple{electron\: microscope}$
Illuminating source is the beam of electrons.

Specimen preparation takes usually takes few days.

Only Dead or Dried specimens are seen.

All lenses are electromagnetic.

It has high resolving power (0.001µm), about 250 times higher  than light microscope.

It has a magnification of 100,000X to 300,000X.

The object is 0.1µm or thinner.

Image is Black and White.

Vacuum is essential for its operation.

High voltage electric current is required (50,000 Volts and above).

It has a cooling system to take out heat generated by high electric current.

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