A&P LAB: Microscopy

What is a compound microscope?

A microscope that uses more than one lens: an ocular lens and objective lenses.

Why is it called a compound microscope?

Because it has more than one lens.

What is the ocular lens?

The lens you look through; it has 10x magnification.

What are the objective lenses?

4x, 10x, 40x, and 100x.

What is the 4x objective lens called?

Scanning power.

What is the 10x objective lens called?

Low power.

What is the 40x objective lens called?

High power.

What is the 100x objective lens called?

Oil immersion; it is not used in this class.

What does the rotating nosepiece do?

It holds all of the objective lenses.

What is the stage?

The part of the microscope where the slide goes; it can move up, down, left, or right.

What do slide clamps do?

They hold the slide in place.

What does the coarse adjustment knob do?

It is the larger focus knob and should be used first.

What does the fine adjustment knob do?

It is the smaller focus knob and should be used last.

What does the iris diaphragm control?

The amount of light going through the sample by controlling the aperture size.

What is the substage light?

The light source for the microscope.

What controls the intensity of the substage light?

The knob on the side of the microscope.

How should you carry a microscope?

With two hands: one hand on the arm and one hand on the base.

Why should you use two hands when carrying a microscope?

For safety reasons and to prevent dropping the microscope.

What should you do before putting a slide on the microscope?

Make sure the stage is all the way down and the scanning objective is in place.

How should the slide be positioned on the microscope?

The labeled side should be up and on the left, and the slide should fit snugly inside the clamps.

Which objective should you start with when using a compound microscope?

The scanning objective (4x).

What should you use to locate the object on the slide?

Scanning power and the stage adjustment knobs.

Which focus knob should you use first?

The coarse adjustment knob.

Which focus knob should you use second?

The fine adjustment knob.

What should you do after focusing the specimen?

Change the objective lens as needed.

What is total magnification?

The magnification produced by the ocular and objective lenses together.

What is the formula for total magnification?

Ocular x Objective = Total Magnification.

What is the total magnification with a 10x ocular and 4x objective?

40x.

What is the total magnification with a 10x ocular and 10x objective?

100x.

What is the total magnification with a 10x ocular and 40x objective?

400x.

What is working distance?

The distance from the top surface of the slide to the tip of the objective lens.

What unit is working distance measured in?

Millimeters (mm).

What is field of view?

The area or diameter of the slide visible when looking through the microscope.

What happens to the field of view when magnification increases?

The field of view decreases.

What happens to the field of view at lower magnification?

The field of view is larger.

What happens to the field of view at higher magnification?

The field of view is smaller.

How can you measure field size at low power?

By laying a ruler where the slide would go and measuring the field.

Why can’t you simply measure field size at higher magnifications?

The field of view becomes smaller due to increased magnification.

What is the field-of-view equation?

Diameter of Field A x Magnification of Field A = Diameter of Field B x Magnification of Field B.

How do you solve for an unknown field diameter?

Diameter B = (Diameter A x Magnification A) / Magnification B.

If the diameter of Field A is 3,500 mm at 40x, what is the diameter at 100x?

1,400 mm.

What should you do when finished using the microscope?

Remove the slide, lower the stage, put the scanning objective in place, wrap the cord, and carry it back using the arm and base.

What is the easiest way to remember the order for focusing?

Start with scanning power, locate the object, use coarse focus, then fine focus, and increase magnification as needed.