Lab 3-1 Introduction to the Light Microscope PDF

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Lab 3-1 Introduction to Light Microscope Laboratory Report Sheet Read pages 141-148 in the Microbiology Laboratory Theory and Application Manual and watch the MicroLab Tutor: Microscope video (10 min 50 sec) at Mastering Microbiology website to learn about the compound light microscope. Then answer the following questions. In addition, you will be asked to demonstrate you can focus a slide under a virtual compound microscope.

Lab Questions 1. Why is a light microscope a valuable tool for microbiologists? Microscopes help the scientists to study the microorganisms. It is one of the most important diagnostic tools when examining the specimen. 2. Why are stains commonly used to help view specimens under the microscope? Some stains can penetrate cell walls and highlight cell components, and this helps scientists visualize metabolic processes. Stain helps us get a better look at the specimens. 3. Label the parts diagram on the diagram of the microscope found below.

Word bank: arm

head

coarse adjustment knob

light source

base

mechanical stage control knob

stage clips

objective lenses

light intensity(rheostat)

eyepiece

fine adjustment knob stage revolving nosepiece

condenser

A.Eyepiece B.Revolving nosepiece C.Objective Lenses D.Stage clip E.Stage F.Condenser G.Light source H.Base I.Light intensity(rheostat) J.Mechanical Stage control knob K.Fine adjustment knob L.Coarse adjustment knob M.Arm N.Head 4. Complete the table below to summarize the functions of each part of the light microscope. Microscope Part

Function

Eyepiece

Observations are made through the ocular lens

Nosepiece

The rotating pieces for the objectives lenses

Objective lenses

Adjustable lens system of different magnifying and power

Arm

Vertical portion of the mircoscope connecting the head and base

Base

Support the microscope

Light source

to illuminate the object evenly

Mechanical stage control knobs

Controls the stage

Stage

The platform that the slide rest on when being viewed

Condenser

Substage lens that puts the light onto the specimen

Coarse adjustment knob

Use to focus on the specimen

Iris diaphragm lever

controls the amount of light to pass through

Fine adjustment knob

Use for precise focusing once coarse is adjusted

Stage clips

The clips that hold the slides on the stage.

5. Using the picture above to help you explain resolution and describe the limit of resolution. The apparent distance of the car headlights seems to blurry and very close to each other because we are limited to the resolution of the human eye. 6. Why is immersion oil used with the oil immersion lens? Oil immersion is a technique used to increase the resolving power of a microscope. The oil is a transparent oil of high refractive index which helps the aperture of the objective lens which will result in a better resolution. 7. What is the limit of resolution for the light microscope? Resolution would improve when the resolution gets smaller. The best resolution by light is about 0.2 µm.

8. How do you calculate total magnification of the specimen being viewed under the microscope? Provide a sample calculation as well. To calculate the total magnification of the light microscope multiply the magnification power of the eye lens by the power of the objective lens. For example, a 10x eye lens and a 100x objective would have a 1000x total magnification.

UD Virtual Compound Microscope Visit the UD Virtual Compound Microscope website to learn the steps required to bring a specimen into focus under the compound light microscope. After you complete the tutorials, you be asked to select a slide and bring into focus using the virtual microscope. When you have brought your slide into sharp focus, take a picture of the image with your cell phone or digital camera. Insert the picture of your sharply focused specimen into the place holder below....