Lab 6 - Microscope

Question 1

what is the purpose of using a microscope?

Answer 1

to view microscopic organisms and agents that are too small to be seen with the naked eye.

Question 2

what is the fxn of the condenser?

Answer 2

to focus the light on the specimen

Question 3

what is the magnification of the ocular lens?

Answer 3

10x

Question 4

what is our limit for detection?

Answer 4

for naked human eye is 100 um

Question 5

what is the average size of a bacterial cell?

Answer 5

1 um

Question 6

if you had a bacterial cell that was 0.01 um, what is the minimum magnification you need to view this cell?

Answer 6

formula to calculate the minimum magnification needed to view this cell that is 0.01 um:
limit of detection / object size. SO 100 um/0.01 um = 10,000 (now you can see it; but we cant achieve this magnification in this lab).

Question 7

define resolution

Answer 7

the minimum distance that two separate objects can be distinguished (objects closer than this distance will be blurred together)

Question 8

in a light microscope, objects closer than 200 nm will…

Answer 8

blue into one blob

Question 9

what is the working distance?

Answer 9

the distance between lens and object

Question 10

lenses with small working distance (40x) collect more…?

Answer 10

lenses with small working distance (40x) collect more LIGHT transmitted from the specimen and hence have a higher resolution than other lenses (10x).

Question 11

why would poor resolution be an issue with the 100x objective lens?

Answer 11

if it is used dry. (since it is a wet lens)

Question 12

how would you solve the poor resolution issue with a 100x objective lens?

Answer 12

by using oil immersion with the 100x objective lens; only place one drop

Question 13

what are the steps of focusing on a microscope?

Answer 13

• Start with the stage up and the light turned low (then turn the light between 4 and 5)
  -Start with the 10x objective lens for bacterial slides.
  -Coarse focus on the specimen.
  -Center an interesting area.
  -Rotate the revolving nose piece to the 40x objective lense. DO not rotate the actual lens itself.
  -Now you the fine focus to focus on the specimen.
  -Place a drop of oil on the slide and rotate the 100x objective lens into place by using the revolving nose piece.
  -fine focus the specimen and turn the light up.

Question 14

what is the Oops! Technique?

Answer 14

A technique that allows you to refocus a slide that already has oil on it without dragging the 40x objective lens through the oil (since it is a dry lens).
-From the 100x objective lens, rotate to the 4x lens, than to the 10x lens.
-Coarse focus the specimen on the 10x lens.
-Rotate back through the 10x and 4x lenses.
-Place another drop of oil on the slide and rotate the 100x lens into place.
-Fine focus the specimen

Question 15

what are the cleaning procedures?

Answer 15

-Do not clean the 4x lens since it doesn’t protrude.
-Start by cleaning the 10x lens with lens cleaner and lens paper. Not kimtech wipes or paper towers.
-Clean the 40x lens with lens cleaner and lens paper.
-Clean the 100x lens with lens cleaner and lens paper.
-Celan the ocular lenses with lens cleaner and lens paper.
-Another other oily/dirty part of the microscope like the stage can be cleaned with lens cleaner and regular tissue paper.

Question 16

what are the closing procedures?

Answer 16

-Move the stage ALL the way down
-Rotate the 4x objective lens into place.
-Turn off the light switch and dial the rheostat knob to 4.5
-Unplug the microscope and bunch the cord.
-Store it in the cabinet with the oculars facing forward.
-When using the prepared slide, clean it with lens cleaner and tissue paper or kimtech tissues.

Question 17

if the specimens are purple, what type of bacteria are they? how about pink? what are the two shapes of colony morphology that we witnessed in class?

Answer 17

-Purple: Gram-Positive.
-Pink: Gram-Negative.
We had rods or coccus.

Question 18

what are the 7 rules of microscopy?

Answer 18

1. Always carry the microscope with 2 hands, one under the base and the other on the arm. (so you don’t drop it).
2. Reposition the microscope by picking it up; never slide the microscope across the bench. (so that you don’t damage the microscope or the slide).
3. Turn off the microscope when not looking through the objective for more than 30 seconds. (so you don’t drain it).
4. When using the 40x and 100x objectives, use only the fine focus; never use the coarse focus with the 40x and 100x objectives. (bc you already focused it, so it should only need slight tweaking).
5. Change to the low power 10x (scanning) or 4x (objective) before lowering the stage. (so you don’t damage the slide).
6. Lower the stage before removing the slide. (“).
7. Clean the lenses with lens tissue only; never clean lenses with Kimwipes or paper towels. (self-explanatory).