Lab 1: Microscopes Flashcards
Occular lens
Both
Lens located inside eyepiece that is used to magnify specimen
Objective lens
Both
Lens located on the nosepiece above the stage that maginify the specimen.
Arm
Both
Used for hand grip while carrying instrument
Coarse focus knob
Both
Roughly focuses specimen by changing the distance between objective lens and specimen.
Light source
Both
Emits light onto specimen
Blue filter
Both
Increases resolution by reducing wavelength of light.
Mechanical stage and mechanical stage knobs
Compound
- Supports the slide/specimen over the hole that admits light from below.
- Moves slide around the stage surface.
Fine focus knob
Compound
Sharply focuses specimen by precisely changing the distance between the obj lens and specimen.
Condenser and condenser adjustment knob
Compound
- Contains 2 lens that focus light onto specimen.
- Moves condenser up or down.
Iris diaphragm and iris diaphragm lever
Compound
- Regulates amt of light passing through condenser.
- Opens and closes iris diaphragm.
Lamp switch and lamp intensity dial
Compound
- Turns light on or off.
- Adusts light produced by light source.
Stage
Dissecting
Supports slide/specimen over the hole that admits light from below.
Main switch
Dissecting
Controls supply of power to microscope. Must be “on” for either light to work.
I switch and T switch
Dissecting
- Turns light above specimen on/off.
- Turns light below specimen on/off.
Stage clips
Dissecting
Holds a slide in position over the stage.
What to consider when choosing which microscope to use
- Size of specimen
- Whether specimen is dead or alive.
- Whether you want to see internal or external detail.
Types of specimens seen by compound microscopes. Give examples
- Small and transparent
- Living or dead
- Internal details
E.g. unicellular organisms
Types of specimens seen by dissecting microscopes. Give examples
- Large and generally not transparent
- Living or dead
- External details
E.g. insects and flowers parts.
Types of specimens seen by transmission electron microscopes. Give examples
- Small
- Dead
- Internal details
E.g. viruses and smaller organelles.
Types of specimens seen by scanning electron microscopes. Give examples
- Small
- Dead
- External details
Similarities between TEM and compound microscopes
Can both see internal details.
Similarities between dissecting microscopes and compound microscopes
Can both see living or preserved (dead) specimen.
What is field of view? How do you estimate actual size of specimen?
- Area that can be seen in the circle of light when looking thru the microscope.
- Fraction of field diameter occupied x field diameter.
Resolution
The minimum distance between 2 points that can be separated and still be distinguished as separate units.
Depth of field
The vertical distance that remains in focus at one time.
Contrast
Ability to discern detail in a light micorscope image against the background.
Parfocal lens
Lens that stay in focus when magnification is changed.
How to improve the contrast
- Add a stain to the specimen.
- Adjust light intensity dial or iris diaphragm.
- Adjust the condenser.
What is the relationship between magnification and depth of field?
Negative/indirect relationship.
Magnification. Formula for magnification of a drawing.
- Ability to see details that you wouldn’t be able to see with the naked eye.
- Mag. = size of drawing divided by actual size (units have to be the same).
Compound microscope: magnification of objective lens and field diameter (mm)
Low power: 4x, 4.8 mm.
Medium power: 10x, 1.8 mm.
High power: 40x, 0.5 mm.
Oil immersion: 100x.
total mag. = occular lens x objective lens
Dissecting microsope: magnification of objective lens and field diameter (mm)
Low power: 2x, 9 mm.
High power: 4x, 5 mm.
