OPTICAL/METALLURGICAL MICROSCOPY

LENS:In optics, piece of glass or other transparent substance that is used to form an image of an object by focusing rays of light from the object.

A lens is a piece of transparent material, usually circular in shape, with two polished surfaces, either or both of which is curved and may be either convex (bulging) or concave (depressed).

The curves are almost always spherical, i.e., the radius of curvature is constant. A lens has the valuable property of forming images of objects situated in front of it.

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Single lenses are used in eyeglasses, contact lenses, pocket magnifiers, projection condensers, signal lights, viewfinders, and on simple box cameras.

More often a number of lenses made of different materials are combined together as a compound lens in a tube to permit the correction of aberrations. Compound lenses are used in such instruments as cameras, microscopes, and telescopes.

LENS:

LENS MANUFACTURING

PRINCIPLE OF IMAGE FORMATION IN CASE OF CONVEX LENS w.r.t DIFFERENT OBJECT LOCATIONS

METALLURGICAL MICROSCOPE

Metallurgical microscope unlike biological microscope works on the principle of reflected light microscopy.

The metallurgical microscope is an important tool for metallurgists, with the help of which fine structural details can be studied.

Since the metallographic specimens are opaque to light, the sample must be illuminated by reflected light. The metallurgical microscope is therefore based on reflected light principle.

It has to be appreciated that the biological microscope works on transmitted light principle.

METALLURGICAL MICROSCOPE

It is used to study the topographic or microstructural features on polished and etched surface of magnifications of 1 to 1500x.

PRINCIPLE OF IMAGE FORMATION

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MAGNIFICATION OF MICROSCOPE

There are two types of lens systems in metallurgical microscope (i) Objective & (ii) Eye-piece. The initial magnifying power of objective & eye-piece is engraved on the lens mount.

When a particular combination of objective & eye-piece is used at the proper tube length, the total magnification is equal to the product of the magnifications of the objective & eye-piece.

FUNCTIONS OF OBJECTIVE & EYE-PIECE

Objective lens is used to resolve the microstructural details of the surface of a polished & etched metallic specimen.

Eye-piece is used to magnify the resolved details of the microstructure. It does not further resolve the microstructural details.