Exam 1 Flashcards
Anatomical Orientation
Terminology used when describing the location where evidence was found
1. superior vs. inferior
2. medial vs. lateral
3. dorsal vs. ventral
4. proximal vs. distal
Antony Von Leeuwenhoek
made the simple microscope spheres of ground molten glass
Hans and Zacharias Janssen
3 tube , 2 lense microscope (compound microscope)
Robert Hooke
Invented modern micrscope and used it to see cells
Carl Zeiss
Built microscope with Ernest Abbe, the Stereo-microscope ; Zeiss Microscope
august Kohler
developed Kohler illumination
Kohler Illlumination Steps
- Focus on whats on the slide and make sure condenser 0.5 cm from the bottom of the coverslip
- close the field diaphram until you see a circle
- move condenser up and down until the edges of the circle become sharp like a hexagon
- center condenser
- open the field diaphram
- take out one of the eye pieces and focus the back field by adjusting the substage aperature
Visible light
red: 750-620
orange: 620-580
yellow: 580-570
green: 570-500
blue: 495-450
indigo: 450-425
Violet: 450-380
Electromagnetic spectrum
longest wavelength to shortest; longer equals less energy while shorter means more energy
Converging Lenses
Lenses that produce a real image that you can see, wider middle
Diverging lenses
Lenses that produce a virtual image apart of the image forming plane, thin middle
Lens Formula
1/f = 1/p + 1/q
Magnification formula
m = q/p
Reduction equation
p/q (1/Magnification)
How compound microscopes form images
- Specimen is illuminated from below, this light goes into the objective lens
- Objective lens produce a real, inverted image
- This image form is then inverted again in the microscope tube
- Eye piece magnifies this real image and projects a virtual image onto the viewer’s eyes.
Back focal plane of objective
Plane behind the objective lense
Conjugate focal planes
optical planes responsible for image forming and illumination
List the Image-forming ray planes that should be in conjugate focus in order to ensure good Kohler illumination.
Field diaphragm, specimen, eyepiece field stop, and retina or the eye or film plane.
List the Illuminating-forming ray planes that should in conjugate focus in order to ensure good Kohler illumination.
Light source, substage condenser, aperture diaphragm, the back focal plane of the objective lens and eyepoint of the eyepiece.
Least distance of vision?
25 cm.; least distance which the eye can see
Stereoscope
to help view at two images separately
Angular Aperture
maximum angle made by the image forming light rays
Infinity optics
When light rays pass though the objective lens and become parallel light ray, this then allows for optical components to be added without affecting the image formation.
Color temperature
color characteristics of light based on temperature, warmer is redder while hotter is bluer
Numerical Aperture (NA) + resolving power
the lenses ability to capture light from the specimen and use it to make an image off certain angles.
- Tied with resolving power, higher resolving power means higher NA is desired
NA equation
NA = nSin(AA/2)
NA= nsinu
n = refraction
u = angle formed
aa = angular aperture
Field Diaphragm
limit the area of illumination to the part of the image field actually being viewed
Condenser
provides converging cone of light through the specimen
substage aperture
allows control of specimen contrast and image quality by controlling angle of illumination
Objective lens
capture light emitted or reflected by the specimen
Ocular lens
magnifies image produced by the objective so you can see it
Plan
Flat field optical corrections
Oil
Oil immersion
N.A
Numerical aperture
Infinity symbol
infinity corrected tube length
Cover glass thickness
0.17 mm
Working Distance
distance between objective front lens and the cover slip, WD decrease, magnification increases
Tube Length
length of microscope body tube from nosepiece to objective, usually 160 mm
airy’s disk
sin (a) = 1.22(lambda)/ When light hits a perfectly circular aperture, a bright central peak forms, followed by a series of rings that decrease in brightness)
Abbe’s rule of thumb
maximum useful magnification equals NA*1000, excess results in empty magnification
Max and min magnification formulas
max: NA * 1000
min: NA * 500
Index of Refraction equation
RI = Speed of light in air / speed of light in substance
Snell’s law
n = sin(i)/ sin(r)
Refraction is when
light passes from one medium through another.
specular vs diffuse reflection
specular is on smooth surfaces and light rays reflect at the same angle. Diffuse is on rougher surfaces and scatters light rays in different directions
Refraction
Bending of light through a medium into another due to a change in the speed of light ray or the wave
Dispersion equation
Nd-1/Nf-Nc
Critical Angle
smallest incident angle where inflection occurs
Dispersion Curve
refractive index vs wavelength, at some point the grain and oil intersect
Becke line dispersion
Higher RI particle than medium, line moves inwards. Lower RI than medium then line moves outwards
Oblique illumination method
When you cover half of the field diaphragm and see where the shadow lies. RI on same side means particle is higher while on opposite side means RI is lower.
Resolution
optically distinguish two points when they’re close together
Calibrated ocular micrometer
micrometers per ocular scale division
Stage micrometer
Slide with with the ruler on it
GRIM 3
modern microscope used in most crime labs
Aberration
changes in focal points based on where waves entered
Spherical aberration
Focal points change depending where light enters the lens, light rays entering farther away from the center are unable to converge at a focal point therefore causing a fuzzy image.
Chromatic Aberration
Each color refracts differently
Curvature of Field
Image is focused on one particular plane and produced a curved image. can be corrected using an expensive lens or the poor man’s method (closing down in the edges)
Barrel Distortion
Barrel magnification decreases as you go out
Pin cushion distortion
Magnification increases as you go out
Astigmatism
eye is shaped different internally which causes light to bend differently when it enters your eyes.
Diffraction equation
n(lambda)=dSin(theta)
Abbe’s diffraction Theory of Image Formation
(0.5)(lambda)/NA
- image is formed by the diffraction of light waves from an object. More diffracted orders means more resolution.
Lord Rayleigh’s Criteria
0.61(lambda)/NA
- standard for determining the the minimum resolvable detail in an optical device
- How should you measure the thickness of a strongly trilobal fiber?
You measure from the middle to the ends.
