A&P Lab Exercise 3 The Microscope

Oil immersion

The longest of the objective lens and has the greatest magnifying power (100X). total magnification is a 1000x

increasing

The microscope field decreases with _______ magnification

Stage

The platform that the slide rests on while being viewed. The stage has a hole in it to allow light to pass through the stage and through the specimen.

Say you are observing an object in the low-power field. When you switch to high power, it is no longer in your field of view. Why might this occur? What should you do initial to prevent this from happening.

a) This occurs because in low power you have a wider field of view, If you switch to high power it narrows your field b) Its important to center the object you want to view as much as possible before switching to a higher power

Nosepiece

carries the objective lenses; rotates so that the different objective lenses can be brought into position over the specimen

mechanical stage

controls the movement of the slide on the stage

Condenser

delivers a concentrated beam of light to the specimen

In general, the more light delivered to the objective lens, the ________ the resolution.

greater

Coarse adjustment knob

knob that allows you to make large adjustments to the height of the stage to initially focus your specimen

Fine adjustment knob

knob used for precise focusing once the initial focusing has been completed

ASSUME THERE IS AN OBJECT ON THE LEFT SIDE OF THE FIELD THAT YOU WANT TO BRING TO THE CENTER (THAT IS, TOWARD THE APPARENT RIGHT). IN WHAT DIRECTION WOULD YOU MOVE YOUR SLIDE?

left

(Indicate the probable cause of the following situations during use of a microscope) the visible field does not change as the mechanical stage is moved

most likely there is physical contact between the slide and the objective lenses.

IF A MICROSCOPE HAS A 10X OCULAR AND THE TOTAL MAGNIFICATION AT THE PARTICULAR TIME IS 950X, THE OBJECTIVE LENS IS USE AT THE TIME IS

objective lenses = 95x

stage

platform on which the slide rests for viewing

The depth of field______ as one moves to higher magnification with the microscope.

Decreases

The working distance ______ as one moves to higher magnification with the microscope.

Decreases

Working distance

Distance from the bottom of the objective lens from the surface of the slide

(T/F) When focusing on high power, always use the coarse adjustment knob to focus

F, only use coarse adjustment knob with the scanning objective lenses

T/F the microscope lens may be cleaned with any soft tissue?

False only special grit free lens paper to clean lenses Grit-free lens paper

(T/F) the microscope should be stored with the oil immersion lens in position over the stage

False, microscope should be stored in the scanning objective lense

Mechanical stage

Holds the slid in position for viewing and has two adjustable knobs that control the precise movement of the slide

The amount of light needed ______ as one moves to higher magnification with the microscope.

Increases

The resolution _____ as one moves to higher magnifications with the microscope.

Increases

Ocular lens

Lens located in the eye piece at the superior end of the head. Most of these lenses have a magnification power of 10X.

Objective lenses

Lenses attached to the nosepiece. Usually, a compound microscope has 4 of these: scanning, low power, high power, and oil immersion.

Parfocal

Slide should be in focus (or nearly so) at the higher magnifications once you have properly focused at the lower magnification

Condenser

Small non magnifying lens located beneath the stage that concentrates the light on the specimen. It may have a knob that raises and lowers it to vary the light delivery. Generally, the best position is close to the inferior surface of the stage

(Indicate the probable cause of the following situations during use of a microscope) Only half the field is illuminated

there is most likely a block in the the light path

Histopathology is the use of microscopes to view tissues to diagnose and track the progression of disease. Why are then slices of tissue ideal for this procedure?

thin slices are ideal because you can see the different layers of tissues and makes it suitable for examination

Why should the light be dimmed when looking at living (nearly transparent) cells?

to provide more contrast

(T/F) A coverslip should always be used with wet mounts

true

fine adjustment knob

used for precise focusing once initial focusing has been done

iris diaphragm lever

used to adjust the amount of light passing through the specimen

A student has the high power lens in position and appears to be intently observing the specimen. The instructor, noting a working distance of about 1cm knows the student isn't actually seeing the specimen How so?

when someone is suing a high power lenses you would have a much shorter working distance than 1 cm, instead the working distance would be (x)mm

Explain the proper technique for transporting a microscope

when transporting the microscope hold it in an upright position, with one hand on its arm and the other supporting its base. Do not swing it or jar the instrument.

400X Total magnification of the high power lens

400X

Total magnification of the scanning lens

40X

The magnification of the scanning objective lens

4x

Field of view

Area you see through the microscope

Rotating nosepiece

Rotating mechanism connected to the head. Generally, it carries three or four objective lenses and permits positioning of these lenses over the hole in the stage

A blood smear is used to diagnose malaria. In patients with malaria, the protozoa can be found near and inside red blood cells. Explain why a microscope capable of high magnification and high resolution would be needed to diagnose malaria

A microscope is needed to assure that the protozoa is indeed inside the cell to diagnose malaria

Iris diaphragm lever

A shutter within the condenser that can be controlled by a lever to adjust the amount of light passing through the condenser. The lever can be moved to close the diaphragm and improve contrast. If your field of view is too dark, you can open the diaphragm to let in more light

Resolution

(resolving power) the ability to discriminate two close objects as separate

describe the proper procedure for preparing a wet mount

1) place a drop of saline in the middle of your slide, with your sample. 2) add a drop of staining dye to be alive to see it in the microscope. 3) Hold the cover slip so that the bottom edge touches on side of the drop (a 45 angle) and slowly lower to limit air bubbles. Check slide and use filter paper to get rid of excess fluid

Total magnification of the low power lens

100X

The magnification of the ocular lens

10X

Substage light

Located in the base. The light from the lamp passes directly upward through the microscope.

light control

Located on the base of arm. This dial allows you to adjust the intensity of the light passing through the specimen

Scanning

Objective lens with the lowest magnification. Red

High power

Objective lens with the second greatest magnifying power (40X). Blue

Low power

Objective lens with the second lowest magnification. Yellow ( magnification = 10x)

Base

The bottom of the microscope. Provides a study flat surface to support and steady the microscope

greater

The depth of field is _______ at lower magnifications

Depth of field

The thickness of the plane that is clearly in focus

Total magnification

This is equal to the power of the ocular lens multiplied by the power of the objective lens used. Ex: ocular lens magnification=10x and objective lens mag.=45x, ____________ is 450x.

(T/F) when beginning to focus, use the scanning objective lens

True

Arm

Vertical portion of the microscope that connects the base and the head.