Magnification and resolution of microscope

1. Presentation of
Micro-Biology

2. Topic:
Magnification and resolution
of microscope
Presented by: Amna Shahzadi
Roll no: 854(023816)
BS zoology(semester 7)
Professor Sir Fazal Illahi Butt

3. Important terminologies
01
02
03
A microscope is a laboratory instrument
used to examine objects that are too
small to be seen by the naked eye.
MICROSCOPE
Microscopy is the science of investigating
small objects and structures using a
microscopic.
MICROSCOPY
The increase in size of optical image over
the size of the object being viewed.
MAGNIFICATION

4. Important terminologies
04
05
06
The ability to distinguish two adjacent
points as distinct and separate.
RESOLVING POWER
Numerical aperture is a number that
expresses the ability of a lens to resolve
fine detail in the object being observed.
NUMERICAL APERTURE
Resolution The smallest distance by whic
h two objects can be separated and still b
e visualized as separate objects.
RESOLUTION

5. Magnification
Increase in apparent size
Naked Eye 4X magnification 6X magnification
8X magnification 10X magnification 12X magnification

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7. Magnification vs. Resolution
Insert the title of your subtitle Here
Magnification
Magnification is the factor by
which an image appears to
be enlarged. It will be a whole
number greater than 1 and is
usually followed by an “x”, as
in 10x magnification.
Resolution is the shortest distance
between two points that can still be
visually distinguished as separate.
The resolution of a typical unaided
human eye is about 200 µm. Using a
microscope decreases the
resolution to distances as short as 0.2
µm. Resolution is a property of the
eye..
Resolution

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9. Resolving Power
Mere increase in size (greater magnification) without
the ability to distinguish structural details (greater
resolution) is not beneficial. To state it differently, the
largest magnification produced by a microscope may
not be the most useful because the image obtained
may be unclear or fuzzy. The more lines or dots per
unit area that can be seen distinctly as separate lines
or dots, the greater is the resolving power of the
microscope system. The resolving power of a
microscope is a function of the wavelength of light used
and the numerical aperture (NA) of the lens system.
Explanation

10. Numerical Aperture
The angle 0 subtended by the optical axis and the outermost rays still covered by
the objective is the measure of the aperture of the objective; it is the half. aperture
angle (Fig. 4-3). The magnitude of this angle is expressed as a sine value. The sine
value of the half-aperture angle multiplied by the refractive index n of the .medium
filling the space between the front lens and the cover slip gives the numerical
aperture (NA): NA = n sin 8 With dry objectives the value of n is 1, since I is the
refractive index of elk When immersion oil is used (Fig. 4-3) as the medium. n is
1.56, and if 0 is 5" then
NA = n sin 8 = 1.56 x sin 58° = 1.56 x 0.85 = 1.33
Na for drive object is less than 1.0,oil immersion objectives have an NA value
greater than 1.0
FOR WATER n =1.33
FOR OIL n = 1.56
Explanation

11. Limit of Resolution
The limit of resolution is the smallest distance by which two objects can be
separated and still be distinguishable as two separate objects. the greatest
resolution} in light microscopy is obtained with the shortest wavelength of visible
light and an objective with the maximum NA. The relationship between NA and
resolution can be expressed as follows:
d =λ/(2NA)
where d = resolution and λ = wavelength of light.
Using the values 1.3 for NA and 0.55 µm, the wavelength of green light, for X,
resolution can be calculated as
d = 0.55 2 x 1.30
= 0.21
From these calculations we may conclude that the smallest details that can be seen
by the typical. light microscope are those having dimensions of approximately
0.2 µm.
Explanation

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