Microbiology Lab 3: Microscopy

Using an oil immersion objective lens allows for what?

higher magnification

What is important to remember when using oil immersion?

immersion oil can only be used with the 100x objective, and without it, the image is blurry

Resolution

the ability to distinguish fine detail

Contast

the ability to distinguish objects, such as cells, from the background

Magnification

the apparent increase in image size

What is the advantage of starting with the 4x objective before moving to the 10x and then the 40x objective?

the field of view is larger, and it's easier to focus

How do the coarse and fine focus knobs work on a brightfield microscope?

the focus knobs move the stage up and down

Total Magnification

the overall enlargement of the image of a specimen. To calculate total magnification, multiply the magnification of the ocular lens (10X) with the magnification of the objective lens.

Why should the fine focus knob typically be used with the 10X and 40X objective lenses?

the slide should be close to in focus after focusing at the 4x objective. Focusing with the coarse focus knob would result in too large a change in focus

What is the total magnification of a specimen using the 40x objective?

the total magnification would be 400x

What is the goal of microscopy?

to create a magnified image of objects too small to be seen with the eye alone

What is oil immersion?

-used on 100x power objective -when a drop of immersion oil is added to the slide, contacting both the sample and objective -without this oil, some of the peripheral light that passes through the specimen is scattered into air or the slide, decreasing resolution.

What is the correct order of steps to view a specimen at 40x magnification on a brightfield microscope?

1. click power switch to turn light on 2. adjust light to appropriate brightness 3. focus at 4x using coarse focus knob 4. adjust ocular lenses to view one image 5. focus using fine focus knob 6. adjust the stage to move the star to the center of microscope view 7. put 10x objective in place 8. focus using find focus knob 9. put 40x objective in place 10. adjust using fine focus knob

What do brightfield microscope use?

a combination of glass lenses and light to view the specimen

Which of the three factors affecting image quality is altered by the light source?

contrast