5: Microscopy, Mitosis, & Statistical Analyses

Compound Microscope

Key instrument in biology, precision-made instrument

Path of Light

Begins from built-in light source controlled by rheostat, directed upwards by mirror through base illuminator lens

Rheostat

Electrical instrument used to control current by varying resistance

Stage

Platform slide sits on

Substage Condenser

Above base illuminator, below stage, series of lenses that focus light onto specimen

Iris Diaphragm

Above base illuminator, below stage, attached to condenser, series of thin overlapping metal plates that can be opened/closed by attached lever, controls amount of light reaching specimen, closing increases depth of field + increases contrast of picture obtained, opening washes out picture

Objective Lens

After specimen, 4 that are rotated into viewing position, shortest to longest is 4x, 10x, 40x, 100x

Scanning

4X, red

Low Power

10X, yellow

High Power

40X, blue

Oil Immersion Lenses

100X, white

Magnification & Numerical Aperture

Written on each lens, lens color-coded with band for easy identification

Ocular Lenses

After objective lens, adjustable, together/apart to accommodate distance between different sets of eyes, each lens can be focused independently to account for differences in vision between 2 eyes on same individual, add additional 10X magnification

Glasses

If for near/far-sightedness, don’t need as focus adjustments to lenses of scope will account for vision issues

Focusing Scope

Use coarse + fine adjustment knobs on side of arm near base, larger is coarse adjustment (4X), smaller for fine adjustment (10x, 40x)

Working Distance

Distance between tip of objective lens + slide, decreases with increasing magnification

Field of View

Diameter of the circle of light seen through scope, decreases with greater magnification

Parfocal

Able to switch between objective lenses with only minor adjustments using fine focus knob, adjust only fine focus each move to higher magnification

Direction of Movement

Left v. right, reversed, object moving left through lens = stage moving right

Human Eye

Limited depth of focus, so do lenses

3D Object

Only part of object on horizontal plane will be in sharpe focus while above and below of plane slightly out of focus/not in focus

Depth of Focus

Decreases as magnification of objective lens increases