Part 1: The Microscope
Identify all parts of the microscope listed in Lab Exercise 2 (Lab Manual) and know their function.
Objective Lenses: A few of the microscopes may have 4 objective lenses, with the largest labeled 100. Do not use this lens! It is an oil-immersion lens and requires a drop of oil between the lens and the slide.
Light Dimmer Switch: In addition to the main on/off switch to turn on the light, you can also adjust the intensity of the light using the light dimmer dial on the left side of the base (if the stage is facing you). If you turn on the scope and you don't see any light (and it is plugged in!), try turning this dial to increase the light intensity. It is usually best to turn down the brightness somewhat while using scanning or low power objective lenses, but you may need to increase light intensity under high power magnification due to the decrease in working distance and much smaller field of view.
Condenser: The condenser is situated directly beneath the stage, and concentrates the light onto the specimen. It can be adjusted (raised and lowered) with the control knob on the left side of the stage. Adjusting the condenser allows you to improve the sharpness of the image. If you have a bright spot (part of the field of view is brighter than the rest), try lowering the condenser a bit.
- The condenser has some additional controls: The condenser has an internal iris that adjusts the size of the opening through which light passes; it is controlled by a small black lever that slides back and forth on the front of the condenser. Although it can be used to adjust the amount of light reaching the specimen, its primary function is to adjust the contrast of the image: opened up (more light) will produce less contrast which may make fine details difficult to see; closed down (less light) increases contrast, but can produce ghosting. To only control the brightness, use the light dimmer dial.
- There are also a pair of condenser alignment screws projecting from the front of the condenser that align the condenser directly beneath the objective lenses. You should not adjust these. If you notice that not all of your field of view is lit (there may be a dark crescent toward one edge), ask your instructor for assistance.
You will be expected to demonstrate your ability to correctly use the microscope during Lab Exam 1.