The Microscopy Series: Polarizing Microscope

Light like other forms of electro-magnetic radiations normally vibrates in all directions. The #PolarizingMicroscope utilizes #PolarizingFilters which selects light that vibrates in a single plane. Lets look into the #optics involved.

Image courtesy: QS Study

Principle

#PolarizingFilters filters help provide information about cellular structures that are composed of well-oriented #Polymer made up of different molecules with different refractive indexes. This makes plane polarized light to travel through those molecules with different velocities in different directions. This property is called #Birefringence. As a result these structures look darker or #anisotropic when illuminated with plane-polarized light.

Image courtesy: Molecular Expressions

Components

1. Polarizer: This first filter made up of #NicolPrism is placed just below the specimen stage with its #VibrationAzimuth fixed in the East-West direction. It allows a single plane of light to pass through it which vibrate only in one direction.

2. Analyzer: The second #filter made up of #NicolPrism is aligned with a #vibration direction oriented North-South, placed between objective and eye-piece. Placed at right angle to the #Polarizer, it helps analyze the direction of #polarization of the #beam,

3. Compensator (Retardation plates): These are placed between the crossed filters to enhance optical path differences in the specimen.

4. Objective Lens: These are strain-free and with anti-reflection coating.

5. Condenser: This is also strain-free and equipped with a #Receptacle for the polarizer. It converges the rays to the object or specimen.

6. Eye piece: Fitted with cross-wire #Reticle or #Graticule, it marks the center of the field view.

Merits

1. #Minute analysis of sample possible specific to the fibers.

2. #Quick, requires little sample preparation.

Demerits

1. Even with phase-polar illumination, not all the fibers present may be seen.

2. Requires great degree of #sophistication on part of the user.

3. Since it analyzes only a tiny amount of sample, #SampleBias or #FalseResults could be an issue.

Applications

1. Visualization of #subcellular structures composed of aligned elements.

2. Studying behaviour of #birefringent structures of the components of contracting muscles.

3. Studying shape regularity and #RefractiveIndex of cell and tissues.

4. #Histological study of qualitative nature of orientation of molecules.

#HailtotheGoodGenes

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