Lab 1- Visualizing Microbes: Microscopy Basics

Bright field Microscopy

• Used to observe objects (microbes) too small to be seen with the unaided eye

Total Magnification formula

• Total Magnification= Ocular Mag x Objective Mag

Resolving Power

• Minimum distance that two objects can be seen as separate

Resolving Power Formula

RP= λ/ ( 2 x Numerical Aperature)

Parfocal

• Remains in focus as you change objectives

Parcentric

• Center of the field of view remains in center of field of of field for all magnification

Working Distance

Distance between the objective lens and slide when in focus

As magnification of the lens increases…

working distance decreases

Immersion Oil

• Used with the 100x objective lens only

• Minimized refraction of light away from lenses to improve resolving power

6 common microorganism shapes we will see

1. Coccus

2. Rod (bacillus)

3. Spirilium

4. Stalk and Hyphs (appendaged bacteria)

5. Filamentous Bacteria

Microscopes are used to see objects that are __________.

• too small to be seen with the unaided eye

The course focus is use to make___________ adjustments, while the fine focus is used to make __________ adjustments to the height of the slide.

• large, small

If you use a 40x objective what is the total magnification

• 400x

Define resolving power

• Minmum distance between two objects that they can still be observed as 2 separate objects

You are viewing a specimen in focus at 10x and when you change to the 40x objective the specimen is now slightly blurry. What should you do to ensure you could see your specimen clearly with the new objective

• Adjust the fine focus until the speciman is sharp and clear

The working distance for the 10x objective will be  __________ than the working distance with the 4x objective

• Smaller

When do you use immersion oil and what is its purpose?

• On the 100x objective, minimizes refraction of light away from the lens