Microscopy

Question 1

condensor

Answer 1

focuses light on the specimen

is focused when:

• -all the light it emits hits the specimen
• -all the light it emits enters the objective

Question 2

parfocal

Answer 2

in focus switching from one objective to another

Question 3

focusing the condensor

Answer 3

close the field diaphragm all the way, adjust condensor focus knob until image is as crisp as you can get it

Question 4

phase contrast

Answer 4

shows degrees of density as degrees of darkness

light is slowed when it passes through dense material in the specimen and emerges with its waves delayed relative to light that missed the dense material. light that missed the dense material is combined with light that passed through it. the waves partially cancel each other out and the specimen appears darker than the background.

Question 5

poor man’s phase

Answer 5

used if a microscope does not allow for phase contrast or if the specimen is thick

the condensor aperture (iris diaphragm) is closed all the way and the light source turned up to compensate. Diffraction creates obnoxious halos.

Question 6

darkfield

Answer 6

the condensor creates a cone of light that strikes the specimen at such an angle that none directly enters the objective. The only light that can enter the objective is light that reflects off of the specimen. The specimen appears bright against a dark background.