Magnification:
- Magnifying/Focusing
- Figuring Total Magnification
- When viewing a slide through the microscope make sure that the stage is all the way down and the 4X scanning objective is locked into place.
- Place the slide that you want to view over the aperture and gently move the stage clips over top of the slide to hold it into place.
- Beginning with the 4X objective, looking through the eyepiece making sure to keep both eyes open (if you have trouble cover one eye with your hand) slowly move the stage upward using the coarse adjustment knobuntil the image becomes clear. This is the only time in the process that you will need to use the coarse adjustment knob. The microscopes that you will be using are parfocal, meaning that the image does not need to be radically focused when changing the magnification.
- To magnify the image to the next level rotate the nosepiece to the 10X objective. While looking through the eyepiece focus the image into view using only the fine adjustment knob, this should only take a slight turn of the fine adjustment knob to complete this task.
- To magnify the image to the next level rotate the nosepiece to the 40X objective. While looking through the eyepiece focus the image into view using only the fine adjustment knob, this should only take a slight turn of the fine adjustment knob to complete this task.
Return To Top of Page
Microscope: a device for magnifying objects that are too small to be seen with the naked eye.
- Simple microscope: single lens magnifier
- Compound microscope: employs two or more lenses
Parfocal: the objective lenses are mounted on the microscope so that they can be interchanged without having to appreciably vary the focus.
Resolving power or resolution: the ability to distinguish objects that are close together. The better the resolving power of the microscope, the closer together two objects can be and still be seen as separate.
Magnification: the process of enlarging the size of an object, as an optical image.
Total magnification: In a compound microscope the total magnification is the product of the objective and ocular lenses (see figure below). The magnification of the ocular lenses on your scope is 10X.
Objective lens X Ocular lens = Total magnification For example: low power: (10X)(10X) = 100X high dry: (40X)(10X) = 400X oil immersion: (100X)(10X) = 1000X
Immersion Oil: Clear, finely detailed images are achieved by contrasting the specimen with their medium. Changing the refractive index of the specimens from their medium attains this contrast. The refractive index is a measure of the relative velocity at which light passes through a material. When light rays pass through the two materials (specimen and medium) that have different refractive indices, the rays change direction from a straight path by bending (refracting) at the boundary between the specimen and the medium. Thus, this increases the image’s contrast between the specimen and the medium.
One way to change the refractive index is by staining the specimen. Another is to use immersion oil. While we want light to refract differently between the specimen and the medium, we do not want to lose any light rays, as this would decrease the resolution of the image. By placing immersion oil between the glass slide and the oil immersion lens (100X), the light rays at the highest magnification can be retained. Immersion oil has the same refractive index as glass so the oil becomes part of the optics of the microscope. Without the oil the light rays are refracted as they enter the air between the slide and the lens and the objective lens would have to be increased in diameter in order to capture them. Using oil has the same effect as increasing the objective diameter therefore improving the resolving power of the lens.