Lab 3: Care and Use of the Microscope Lab

Compound light microscope

"Light" refers to the method that light transmits the image to your eye. "Compound" deals with the microscope having more than one lens.

Microbes are less than

1 millimeter in size and usually measured in micrometers (1 um= 1/1000 mm)

Calculating diopter values

1) After the interpupillary distance has been determine, find the diopter adjustment rings in the ocular lens 2) turn diopter rings so the mark on each ring aligns with the midpoint of the microscope scale on the ocular 3) close the left eye. Use the fine focus to find the clearest possible image 4) open left eye, and close right eye 5) tuen diopter ring on the left lens from one extreme to the other to find the best viewing place 6) record the diopter value

Calculating interpupillary distance

1) focus on a specimen using lower power objective 2) move oculars apart 3) notice you can see two images. Move the oculars tighter until the split image is viewed as one 4) record the number

12 cells fit across the diameter of the FOV using the low power. Calculate cell size.

1800um/12.0 cells= 150um cell

If you count 5.5 cells that would fit across the diameter of the field of view (FOV) using the scanning objective, what would be the cell size?

4500/5.5= 818.18 You can round it to 820um.

Stage (of microscope)

A flat area that supports the slide.

Discuss the relationship between: magnification, diameter of FOV, and brightness

As magnification increases, FOV decreases & brightness decreases

Discuss the relationship between: magnification, diameter of FOV, and the relative brightness of all objects.

As magnification increases, the diameter of FOV decreases and the brightness decreases.

Condenser (of microscope)

Concentrates light before it passes through the tissue.

Discuss how you would calculate cell size of a single celled organism?

Diameter of FOV/# of cells across FOV

Calculating cell size

Diameter of the FOV/Number of cells across diameter of FOV

How do you calculate cell size?

Diameter of the FOV/number of cells

Compare and contrast dissecting and light microscopes

Dissecting- Low magnification and Large specimen. Compound- High magnification and small specimen. Similarities: Dissecting and compound light microscopes are both optical microscopes that use visible light to create an image. Both types of microscope magnify an object by focusing light through prisms and lenses, directing it toward a specimen. Differences: The Light Microscope is the most commonly used. Magnifies from 40x up to 1,000x. Specimens can be dead or alive. The compound light microscope can be used with a dye on the slide to view tissue samples, blood, microorganisms in pond water, microscopic cells. The microscope allows light to pass through a specimen and uses two lenses to form an image. The dissecting microscope is a light microscope that uses low magnification. Magnifies up to 40x. The dissecting microscope is used to view larger organisms, organs, tissues, and small objects that can be seen with the naked eye but need more magnification to view details.

Calculate total magnification for a particular objective len

Each time by 10 4X=40 10X=100 40X=400

Base (of microscope)

Gives microscope support

Resolution

How clearly details can be seen

Body Tube microscope

Joins the ocular lens and nosepiece

What is the difference between magnification and resolution?

Magnification is how enlarged something is, while resolution is how clearly details can be seen

Ocular lens

Magnifies the image 10x Ocular lens is closer to your eye

Objective lens

Magnifies the object. Scanning objective has a magnification of 4X. Low power has a magnification of 10X. High power has a magnification of 40X

Light microscopes

Microscopes that use light and lenses to magnify the image of a specimen Can magnify an object 1000 Times to 2000 times the original diameter.

Magnification

The degree of enlargement of a specimen

Arm (of microscope)

The pan that you grasp to carry the instrument

nosepiece of microscope

The revolving pan wheee the objectives are attached

Resolution

The smallest distance between two points How clearly details can be seen

When you estimate cell size, you need to take into consideration the objective you are using to view the object with and the diameter of the field of view (FOV).

True Using the Scanning Objective, the diameter of the FOV is 4,500um. Using the Low Power, the diameter of the FOV for is 1800um. Using the High Power Objective, the diameter of the FOV is 450um Using Oil Immersion, the diameter of the FOV is 180um.

As you increase the magnification, you are decreasing the FOV

True. Also, if you know the FOV and the magnification when viewing an object, you can calculate the size of the cell There is a mathematical relationship between the magnification and the diameter of the FOV

Mechanical stage drive knobs

Two knobs below the stage that will move the slide on the stage, giving the observer a total field as she looks through the eyepiece.

Diopter value

When you look through a microscope with two eye-piece lenses, you have to change the focus on one eyepiece to compensate for the difference in vision between your two eyes.

Parfocal

a lens that stays in focus when magnification/focal length is changed

electron microscope

a microscope that focuses a beam of electrons to magnify objects Electron beams have wavelengths 100,000 times shorter than visible light and allows magnification up to 10 million times. Electron microscopes allow viewers to increase magnification without losing resolution. Live specimens cannot be observed with the electron microscope and samples take data rather than minutes.

iris diaphragm

controls the amount of light passing through the specimen

focus adjustment knobs

course adjustment knob for larger focusing and fine adjustment knob for precision focusing

interpupillary distance

distance between eyepieces

objective lens

enlarges the image of the specimen Scanning objective has a magnification of 4X. Low power has a magnification of 10X. High power has a magnification of 40X. Oil immersion lens has a magnification of 100X.

FOV

field of view

light source of microscope

provides light to view image