Microscope Lab

The lab was fun, but my computer did not want to cooperate with saving the whole screen. I took pictures of the screen with the flash turned off on my digital camera...I hope those will suffice.

First off, let's start with the history of the microscope. The first one was created by Zacharias Janssen (possibly begun by his father) in Holland in 1595. The first compound light microscope was just a simple tube with lenses at either end. It magnified from 3x to 9x. Robert Hooke improved on the microscope around 1660. He coined the word cell to describe features of the plant tissue he had seen under the microscope. The Egyptians, however, may have had an idea of some of the concept for what would become the microscope. There were rock crystal artifacts in the shape of convex leses discovered from around 2600 BCE. Max Knoll and Ernst Rusta invented the first electron microscope in 1931 CE.

There are four main types of microscopes. The most commonly used one is the compound light microscope. It is light illuminated and provides a 2 dimensional view of the specimen. It allows the viewer to see individual cells, including live ones. It has a high magnification, but low resolution. Then there is the dissection microscope whic is also light illuminated. It provides a 3 dimensional image. It does not allow the viewer to see individual cells as it has a low magnification power. Another type is the scanning electron microscope whic is electron illuminated. This provides a 3 dimensional image and has both high magnification and high resolution. The specimen has to be coated in gold, and it produces a black and white image. The final type of microscope is the transmission electron microscope, also electron illuminated. It produces a 2 dimensinal image and uses thin slices of the specimen. It also has both high magnification and high resolution.

Here are the slides I viewed during the lab

onion root tip at 40X

bacterial capsule at 40X

cheek smear at 40X

The parts of a microscope are used as follows:

STAGE - this is the platform where you set your slide for viewing. It is easiest adjusted looking at the microscope. You want to lower it to place your slide, then move it to its top position before viewing.

FOCUS KNOBS - There are two of these, located on the side of the microscope, both best adjusted while looking through the microscope. The coarse focus knob adjusts very quickly and the fine focus fine tunes the image and adjusts slowly.

IRIS - the iris controls the amount of light let through to view the specimen. It is located under the stage and is best adjusted while looking through the microscope.

OCULARS - These are the pieces you look through. They need to be adjusted to fit your face. The usual starting position is both of them on 64. You need to look through them to see if they are adjusted properly. It is best to look through these with your eyes 3/4 of an inch above them.

OBJECTIVES- these are the lenses that magnify your specimen. There are usually 4 on a compound light microscope. You always want to start with the 4X objective and then adust upwards. These are best adjusted looking at the microscope.