Brightfield Microscope – Flashcards
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| What is a Brightfield microscope? |
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| A microscope that allows light rays to pass directly to the eye without being deflected by an intervening opaque plate in the condenser. |
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| What is the framework of a Brightfield Microscope made of? |
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| Arm & Base |
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| What is the stage of a Brightfield Microscope? |
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| The horizontal platform that supports the microscope slide. |
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| What is the stage adjustment of a Brightfield Microscope? |
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| A clamping device used for holding and moving the slide around on the stage. |
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| What does the light intensity control do? |
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| It varies the intensity of light. |
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| What does a neutral density filter do? |
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| It reduces the intensity of light below the lower limit allowed by the voltage control. |
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| How many lens systems do compound microscopes have? |
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| 3 |
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| What are the lens systems of a compound microscope? |
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| Oculars, objectives and condenser. |
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| What is the ocular also called? |
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| Eyepiece |
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| What does the ocular consist of? |
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| 2 or more internal lenses |
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| What is the magnification of the ocular? |
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| Usually, 10x |
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| How many objectives are there in a compound microscope? |
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| Usually, 3 or more |
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| Where are the objectives located? |
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| Attached to a rotable nosepiece. |
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| What are the magnifications of objectives? |
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10x (low power) 40x (high-dry) 100x (oil immersion) |
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| How is the TOTAL magnification of a microscope calculated? |
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"power of ocular" x "power of objective"
Eg: 10 x 100 = 1000 (the object is magnified 1000 times its actual size) |
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| Where is the condenser located? |
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| Under the stage. |
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| What does the condenser do? |
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| It collects and threads the light from the lamp to the slide. |
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| What's the difference between the condenser and the other two types of lenses? |
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| It does not affect the magnifying power of the compound microscope. |
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| How can the condenser be moved? |
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Up Down |
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| What does the diaphragm do? |
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| It regulates the amount of light that reaches the slide. |
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| Which are the focusing knobs? |
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Course adjustment Fine adjustment |
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| What are the focus knobs used for? |
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| Used for bringing objects into focus. |
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| How to make diopter adjustments? |
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Focus with the right eye only Turn the diopter adjustment ring until sharp imagine is seen with the left eye as well. |
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| What is the resolving power? |
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It is an intrinsic property of lenses that sets the limit for magnification. ; Also, it is a lens' ability to completely separate two objects in a microscope field. |
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| What is the formula for the resolving power? |
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| d = 0.5 (lambda)/NA |
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| What is NA - Numerical Aperture? |
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| It is a mathematical expression that describes how the condenser lens concentrates and focuses the light rays from the light source. |
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| When is NA maximized? |
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| When the light rays are focused into a cone of light that then passes through the specimen into the objective lens. |
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| What lowers NA? |
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| Loss of refracted light |
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| What is the limit of resolution for any light microscope? |
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| 0.2 micrometers |
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| How large are bacterial cells? |
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| About 1 micrometer. |
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| Why use a blue filter over the light source? |
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| Because the shorter wavelength of the resulting light will provide max resolution. |
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| What are some other things one could do to max resolution? |
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1. condenser: highest position 2. diaphragm: not stopped down too much 3. use immersion oil (100x) |
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| What is special about immersion oil? |
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| Has the same refractive index as glass. |
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| What does the immersion oil do? |
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| It forms a continuous lens system that limits the loss of light due to refraction. |
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| Are magnification and resolution directly proportional? |
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| Yes! |
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| Could one achieve greater magnification by adding a stronger ocular lens? |
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| No! |
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| What should one use to clean the lenses? |
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1. lint-free, optically safe tissues 2. solvents (green soap and warm water, xylene, alcohol and acetone - used sparingly) |
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| What should not be touched in high-dry examination? |
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| The coarse adjustment knob! |
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| What does parfocal mean? |
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| The image will remain in focus when changing from a lower-power lens to a higher-power lens). |
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| What should one do when using the oil immersion technique? |
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1. Use oil immersion oil 2. Open the diaphragm as much as possible 3. Keep condenser at highest point 4. Use blue or green filters |
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| Magnification increases as the working distance of the lens ... |
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| decreases. |
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| Describe the position of your hands when carrying the microscope to and from your laboratory bench. |
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One hand - under the base (to support its weight) Other hand - on the arm (for balance) |
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| What is the limit of resolution of the unaided human eye? |
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| 0.2 mm |
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| What 2 adjustments can be made to the condenser? |
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1. Condenser height 2. Disphragm |
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| What effect do adjustments to the condenser have on the image? |
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| Illumination is increased (when condenser is raised and disphragm is opened) |
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| Why are condenser adjustments generally preferred over the use of the light intensity control? |
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| Condenser adjustments will increase illumination without affecting the bulb life. |
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| Why is it necessary to use oil in conjuction with the oil immersion lens and not with the other objetives? |
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| Because the small working distance does not allow enough light to enter the lens. The oil directs more light into the lens. |
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| The coarse and fine focus knobs adjust the distance between... |
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| the stage and the objective lens. |
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| The most useful adjustment for increasing image contrast in low-power magnification is ... |
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| closing down the diaphragm. |
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| What is the field of view? |
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Area viwed through ocular.
Decreases with increasing magnification |
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| Brightfield is beter used for ... cells. |
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| STAINED |
