Microscopes

A-Revolving Nosepiece-allows the objective lenses to be switched around

B-Objective Lens-the second magnifying lens of a compound microscope. There are usually 3 objective lenses-high, medium, and low powered.

C-Stage Clips-clips that are used to hold a slide in place on the stage.

D-Diaphragm-device that controls the amount of light allowed through the stage.

E-Light Source-provides light through the stage in order to see the specimen. Some microscopes don't have light sources but rather mirrors which are used to reflect light from the surrounding room.

F-Eyepiece-the first magnifying lens of a compound microscope. This is where you look into the microscope.

G-Body Tube-this connects the eyepiece to the objective lenses.

H-Arm-place one hand here while holding the microscope.

I-Stage-place the specimen on the stage under the objective lens.

J-Coarse Adjustment Knob-turning this knob raises or lowers the stage bringing the specimen into focus. Use this adjustment knob while viewing with the low and medium power objectives in place.

K-Fine Adjustment Knob-turning this knob makes very tiny changes in the resolution, bringing the image into sharp focus. Use this adjustment knob mainly on the high power objective.

L-Base-place one hand here while carrying the microscope.

Total Magnification

Magnification refers to how much larger an image appears in a microscope than in real life.

Compound Light Microscopes usually have two lenses. In order to know how magnified an image is (how much larger it appears under the microscope), you must calculate the total magnification.

Total Magnification=Eyepiece x Objective Lens

Most eyepieces make an image appear 10 times larger than normal, so they are said to have 10x magnification. Objective lenses vary in their magnification powers, but they are usually 4x (low power), 10x (medium power), or 40x (high power).

If you are viewing a specimen under high power, your total magnification would be 10x (eyepiece) times 40x (objective lens) or a total of 400x. This means that what you see in the microscope is 400 times larger than the actual size of the specimen in real life.

Using a Microscope

Clear area of extra supplies.
Plug microscope in and turn on light source.
Place specimen on stage. The specimen should be thin enough that light can pass through it.
Adjust the diaphragm so that it is comfortable to your vision.
Using the low-power objective, turn the coarse adjustment knob until the specimen comes into focus. Readjust the diaphragm if necessary.
Center the specimen/slide so the image is in the middle of your field of view.
Turn the revolving nosepiece to switch to the medium power objective lens. Readjust the focus using the coarse adjustment knob.
Center the specimen/slide so the image is in the middle of your field of view.
Turn the revolving nosepiece to switch to the high power objective lens.
DO NOT USE THE COARSE ADJUSTMENT KNOB NOW or you risk breaking the specimen or the objective lens. Use the fine adjustment knob to bring the specimen into focus.
When you finish looking at your specimen, put the low power objective in place and turn the coarse adjustment so that the stage is as far away from the objective lenses as possible. Turn off the microscope and unplug it. Wrap the cord up and put the dust cover on.

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