Azimuth angle. A term used to describe
the orientation of an object in a plane such as the specimen plane of the
microscope. On a graph with polar coordinates marked off in 360°, the angle
subtended between a fixed reference (designated 0°) and a vector rotated about
the origin.
Back aperture of the objective lens. An
aperture plane of the light microscope located at or near the rear lens element
of the objective lens and the site of formation of a diffraction image of the
object. Optical devices such as phase plates, DIC prisms, and aperture masks
used in forms of interference microscopy are located at or near this location.
Background subtraction. An operation in
electronic imaging whereby an image of the featureless background near an
object is subtracted from the image of the specimen to remove patterns of
irregular illumination and other optical faults such as scratches and dust.
Beam splitter. An optical device for
separating an incident beam of light into two or more beams. A prism beam
splitter in the trinocular head of a microscope directs the imaging beam to the
eyepieces and to the camera simultaneously. A polarizing beam splitter made of
a crystalline birefringent material is used to produce linearly polarized
light. A dichroic mirror beam splitter reflects excitation wavelengths while
transmitting long-wavelength fluorescence emission.

Bertrand lens. A built-in telescope
lens located behind the back aperture of the objective lens. When rotated into
the optical path, the back aperture and diffraction plane are seen, and other
planes that are conjugate to it, while looking in the oculars of the microscope.

Biaxial crystal. A class of
birefringent crystals having two optic axes. Mica is an example of this class
of crystals.

Bioluminescence. An oxidative process
resulting in the release of energy as light emission— for example, firefly
luminescence, which requires an enzyme, luciferase, to catalyze a reaction
between the substrate luciferin and molecular oxygen in the presence of ATP.

Birefringence. The double refraction of
light in transparent, molecularly ordered materials caused by the existence of
orientation-dependent differences in refractive index. Also refers to the
refractive index difference experienced by a transmitted ray through such a
material. Incident beams of light on a birefringent specimen are split into O
and E rays that can recombine after emergence from the object, giving linearly,
elliptically, or circularly polarized light.

Brewster’s angle. The unique angle
formed by an incident ray and the perpendicular to a reflective dielectric
substance such as water or glass (the transmitting medium) at which the
reflected ray is totally linearly polarized.

Bright-field microscopy. A mode of
optics employing the basic components of objective and condenser lenses for the
examination of amplitude objects such as stained histological specimens.

Brightness. A qualitative expression
for the intensity of light.

Chromatic aberration. An aberration of
lenses, whereby light waves of different wavelength are brought to focus at
different locations along the optic axis. In the typical case of a simple thin
lens, the focal length is shorter for blue wavelengths than it is for red ones.

Coherent light. A beam of light defined
by waves vibrating in the same phase, although not necessarily in the same
plane of vibration. To maintain the same phase over long distances, coherent
waves must be monochromatic (have the same wavelength). Laser light is
monochromatic, linearly polarized, and highly coherent. 


1 2 15
February 28th, 2014

Know your tool – Microscope

Image distance and object distance. With respect to the principal planes of a lens, the image-to-lens and object-to-lens distances, as […]

February 28th, 2014

Definitions in Microscopy

Diffraction grating. A transparent or reflective substrate containing an array of parallel lines having the form of alternating grooves and […]

February 21st, 2014

Inking the Specimen

INKING THE SPECIMEN ·         Various Water/organic fluids insoluable inks and colored powders can be used to mark critical points on […]

February 13th, 2014

Tissue Sampling Techniques – Small Biopsies & Triaging

Tissue Sampling Techniques – Small Biopsies & Triaging Most Important Steps • Patient identification – Identification on the requisition must […]

February 6th, 2014


(Material Collected From various reliable sources- My role is just assembling facts for you. No intention of claiming this to […]

January 30th, 2014

Previous Year Question Papers of Various universities – For MDS – Oral Pathology

CONNECTIVE TISSUE STAINS 1.     Discuss the CT stains10 mks(RGUHS) 2.     Routine stains used in oral pathology-10 mks(RGUHS) 3.     Discuss stains […]

January 23rd, 2014

Previous years questions from various Indian Universities – for MDS in Oral Pathology

PULP AND PERIAPICAL INFECTIONS Chronic hyperplastic pulpitis- 10 mks Define and classify Osteomyelitis. Discuss in detail non- suppurative OM-10 mks […]

January 16th, 2014

Previous years questions from various Indian Universities – for MDS in Oral Pathology

MISCELLANEOUS IN ORAL PATHOLOGY 1.      Granulomatous infections of the oral cavity- 100 mks (MU) 2.      Oro- facial pain-10 mks 3.      […]

January 9th, 2014

Human Deciduous Mandibular Molar

January 9th, 2014

Previous years questions from various Indian Universities – for MDS in Oral Pathology

CONNECTIVE TISSUE NEOPLASMS 1.       Discuss the neoplastic lesions of bone of CT origin- 20 mks 2.      Classify nerve tissue tumours […]