Microbiology Lab 1
Why is it advisable to start first with the low-power lens when viewing a slide?
The oil immersion lens has the smallest working distance and one runs the risk of striking the slide with the lens when trying to achieve focus. Starting with low power lens, which has a larger working distance, and progressing up to the oil immersion lens is advised.
This objective lens provides the highest magnification.
oil immersion
Differentiate between the limit of the resolution of the typical light microscope and that of the unaided human eye.
Eye= 0.2 mm Light microscope= 0.2 um
Acetone is the safest solvent for cleaning an objective lens.
False
In this course, we ALWAYS flame the mouth of the test tube when transferring cultures.
False
The coarse focus knob can be used to adjust the focus when using any of the objective lenses.
False
The total magnification capability of a light microscope is only limited by the magnifying power of the lens system.
False
A diaphragm is used to regulate light passing through this lens.
Condenser
This lens collects and focuses light from the lamp onto the specimen on the slide.
Condenser
What two adjustments can be made to the condenser?
Height & diaphragm
This objective lens provides the 2nd highest magnification.
High-dry
What effect do these adjustments have on the image(condenser)?
Illumination of the specimen is increased when the condenser is raised and the diaphragm is opened
What is the total magnification if you are using the 40x lens on your microscope, which has 10x ocular?
400x
What is the relationship between the working distance of an objective lens and its magnification power?
As per pf the objective increases, the working distance decreases.
Please name the term used when a microscope remains in focus when changing magnification.
Parfocal
Before the oil immersion lens is rotated into place, you shoul
- Center the objective of interest in the preceding lens. - Place a drop of oil on the slide.
The resolving power of a microscope is a function of
- Numerical aperture of the lenses - The wavelength of light
When using the oil immersion lens, what four procedures can be implemented to achieve the maximum resolution?
1. layer of oil 2. Bulb filter over light source 3. Raising condenser to highest point 4. Opening the condenser diaphragm
The microscope used in this course cost how much?
10,000
Which lens would be the closest to the specimen slide when in focus on your microscope?
100x(aka oil emersion)
The most useful adjustment for increasing image contract in low-power magnification is
Closing down the diaphragm
The coarse focus knob should be adjusted only when using this objective lens.
Low power
This objective lens provides the lowest magnification
Low-dry
Diopter adjustments can be made to this lens.
Ocular
This lens, also known as the eyepiece, often comes in pairs.
Ocular
____x____=Total Magnification on a microscope
Ocular; Objective
What fluid do you use for the 100x lens?
Oil
This objective lens has the shortest working distance.
Oil immersion
Why is it necessary to use oil in conjunction with the oil immersion lens and not with the other objectives?
Oil is used with the oil immersion lens because the small working distance does not allow enough light to enter the lens. The oil, which has the same refractive index as glass, directs more light into the lens (limits the loss of light due to refraction).
Describe the position of your hands when carrying the microscope to and from your laboratory bench.
One hand should be under the base of the microscope to support its weight, and one hand should be on the arm for balance.
The coarse and fine focus knobs adjust the distance between
The stage and the objective lens
Once focus is achieved at one magnification, a high-power objective lens can be rotated into position without fear of striking slide.
True
Only lint-free, optically safe tissue should be used to wipe off microscope lens.
True
How often should you disinfect your benchtop in a normal lab class?
Twice-beginning and end of lab
What is the term used for bacteria that are everywhere?
Ubiquitous
Why are condenser adjustments generally preferred over the use of the light intensity control?
Unlike the voltage control, condenser adjustments will increase illumination without affecting the bulb life.