Microscopy

Question 1

3 main properties of a microscope are?

Answer 1

Good magnification
Good resolution
Good contrast

Question 2

Light field microscope Principal

Answer 2

The rays from light source the passes through iris diaphragm falls on specimen.
. From specimen both reflected and unreflected light pass through the objective to produce a magnified image
And to the ocular lens and the image is further magnified

Question 3

Dark field microscope principle

Answer 3

There is the dark field condenserWhich has a central opaque disAnd an annular hollow areaThe lightOnly the reflected light passes through the objectiveTo the ocular lensThe undeflected lightDoes not pass through the objective

Question 4

Application of dark field microscope

Answer 4

It is used to identify living unstained cells and thin bacteria like spirochetes ‘

Question 5

Phase contrast microscope

Answer 5

In this microscopeContrast is increased It visualisesNon-stained cellsBy creating difference in contrast between cells and water

Question 6

What are spirochetes

Answer 6

Spiral shaped bacteria which are seriously pathogenic to humans example- syphillis, limes disease

Question 7

Principle of phase contrast microscope

Answer 7

1. Condenser is similar to that dark field microscope
2. it produce a hollow cone of light passes through the specimen and ray is deviated by 1/4th of of the l_ wavelength out of phase.
3. The undeviated ray not passing through the cell strikes a phase ring and the deviated ray misses the phase ring
4. The rays from the phase ring will by 1/2 wave length out of phase which will cancel out each other and form an image

Condenser → specimen → phase ring → objectivelens → ocular tens

Question 8

Application of phase contrast microscope.

Answer 8

1. Shap of living cells
2. Microbial motility
3. Detecting microbial internal cellular components like inclusion bodies, spindles chromosomes, cell membrane, nuclei, etc

Question 9

Principle of fluorescent microscope

Answer 9

1. Fluorescent dyes exposed to uv light are said to fluoresce( converts short to long wave length)
2. Light passes through excitation filter → dichromatic mirror→ falls on specimen → the fluorescent dye absorb the light and convert to long wave length → objective → barrier filter → eyepiece

Question 10

Applications of fluorescent microscope

Answer 10

1.epiflourscent microscope
→ auto fluorescence _ example- cyclospora
→ microbes coated with floursent dyes
→ immunoflourscence
2. Confocal microscope

Question 11

Electron microscope was. Invented by

Answer 11

Ernst ruska

Question 12

Specimen preparation steps in transmission electron microscope

Answer 12

1. Fixation- glutaraldehyde
2. Dehydration-ethanol
3. Embedding _ plasticpolymers
   4 slicing-mounted into coppermetal slide

Question 13

Principle of electron microscope

Answer 13

Electron beams → high speed electrons travelling in vacuum → magnetic condensers → sliced specimen in copper slide → objective and ocular magnetic → final image on a photographic film.

Denser region in the specimen scatters more electrons hence appears dark.

Question 14

Applications of electron microscope.

Answer 14

virus detection

→ either directly from clinical specimens, → from tissue culture