Microscopy (Objective 3) Flashcards
Should oil be cleaned from the 100× objective using kleenex?
No
True or false
Working distance increases as numerical aperture and magnification increases?
False
True or False
If a specimen can be focused on 10x but is not in focus when switched to oil immersion objectives, the problem may be due to an upside down slide
True
True or False
To adjust the oculars for the distance between your eyes,use the diopter adjustment on one of the oculars
False
In what position should the swing out lens be in when using high power or oil immersion objectives?
In the light path
The point where all light rays meet at a specific point after passing through a lens is referred to as?
Focal point
How would you correct for spherical aberration?
Combining a strong convex and concave lens and blocking any light rays falling on the margerins of the lens
Which microscope system is responsible for the real,inverted image?
Objective lens system
On the oculars, the K engraving refers to what?
Compensating eye pieces
True or False
Certain objectives are only designed for specific mechanical tube lengths?
True
Which of the following is not a common magnification for an objective lens? 10x, 20x, 50x, or 100x
20x
What magnification is considered a low power lens?
10x
A black ring on the end of an objective or the markings “oi” refers to what?
The objective lens requires oil immersion.
Well, focusing on a specimen initially on low power, you would use the course knob focus first until you see the specimen followed by the use of the fine focus knob until you obtain a clear sharp image.
True or false.
True
True or false once you have focused on low power. When you switch to high power objectives, you should adjust the focus using the course focus mainly.
False
Excess oil should be removed from the oil objectives using lens paper followed by lens, cleaner.
True or false?
True
What lens system is closest to your eyes and provides a further 10x magnification?
Ocular lens system
What magnification level lenses require oil immersion?
50x and 100x
What happens to the working distance (WD) when you increase magnification?
It decreases
If lens A has a numerical aperture of 1.25 and lens B has a numerical aperture of 0.25, what lens would give us better detail?
Lens A
True or false. We use oil to increase the amount of light that enters the objective?
True
What do we mean by the term parcentral when referring to microscopy?
The object remains centered when switching between objectives.
Which part of the microscope should be adjusted to match the numerical aperture on the objective of lens?
The iris diaphragm.
What is the general flow of light through a bright field microscope?
Light bulb, condenser unit, specimen, objectives, body tube, oculars.
What is the total magnification of a specimen that is being viewed under a 40x objective?
400x
True or false
you can increase your resolving power by using a blue filter?
True
The shortest distance between two points that can be distinguished as separate entities is referred to as?
Resolution
What is the main purpose of kohler illumination?
To center and focus the light on the specimen to ensure optimal use of illumination.
When you can focus on 10x but when moving to a higher power objective ( 50x or 100x) times you notice it is impossible to focus. What would you check first?
Check to see if the slide may be upside down.
When setting kholer, you notice that the field of view is not centered when the field diaphragm is closed. What part of the microscope would be used to fix this?
Centering screws
True or False
Both the oculars and the objectives provide magnification of the specimen.
True
What is the main purpose of the condenser lens system?
To focus the light rays onto the specimen by producing a cone of light that evenly illuminates the field.
What is reflection?
Reflection is the returning of light from a surface (“bounce back”)
What is refraction?
Refraction is the bending of light as it passes from one transparent media to another of a different density.
What happens to the speed of light when it travels from a less dense medium to a more dense medium?
Slows down
What happens to the speed of light when it moves from a more dense medium to a less dense medium?
It’s speeds up
What is the formula for the refractive index?
N= speed of light in a vacuum
‐————————–
Speed of light in a given material
What is the R.I. of Air?
1.00
What is the R.I. of water?
1.33
What is the R.I. of glass?
1.52 (1.46~1.92)
What is the R.I. for immersion oil?
1.52
What way will the light bend if the second medium is more dense? (Towards or away from the perpendicular)
Towards the perpendicular.
What way will light bend if the second medium is less dense?
(Towards or away from the perpendicular)
Away from the perpendicular.
What is dispersion?
It is the separation of white light into colored components when light strikes a prism.
In dispersion, what color of light is bent the most?
Violet
In dispersion, what color of light is bent the least?
Red
What is defraction?
It is the spreading out of light rays after encountering an opening.
Is a convex lens positive or negative?
Positive.
Is a concave lens positive or negative?
Negative.
What is the focal point?
The focal point is the spot where the rays of light parallel to the principal access are brought together.
What is focal length?
The focal length is the distance between the lens (optical center) and the focal point.
The inability to focus all color components of light at the same focal point is known as?
Chromatic aberration
Chromatic aberration is caused by what type of lens?
A convex lens causes dispersion into its components, which cause color to be formed at different focal points.
What corrects chromatic aberration?
Combining convex and concave lenses.
Can be further corrected by adding flourite element to the lens.
Achromatic
2 color correction
Apochromatic
3 color correction
What is spherical aberration?
Curvature of a field, it results in a curved image of a flat object
How can you correct spherical aberration?
By blocking light rays from falling on the marginal areas of the lens or by combining a strong positive lens with a negative lens, - the same that is done for chromatic aberration.
Ocular lens system
Producers the final enlarged virtual image seen by our eyes
Objective lens system
Produces the initial enlarged real inverted image of the object
Condenser system
located below the object, it concentrates the light rays on the object
Illumination system
The light source
Mechanical support system
Arm and base of microscope. devices used for focusing and moving the object or a lens system.
Engravings found on the ocular lens system
K or comp - Compensating eye piece, high quality, several lenses, flat field.
Glasses symbol - High point lens for people with glasses.
W - Wide field lens provides a large flat field of view.
PL, F or EF - Flat field optical correction eye pieces.
Periplan - Flat field also compensates for astigmatism and chromatic aberration.
What happens to working distance with increased magnification?
Decreases
What must be changed when you change the objective?
The iris diaphragm NA must match the objectives NA.
What does a black ring on an objective mean?
Oil immersion
What is the purpose of using oil?
Less light is refracted away from the lens, and more light will enter the objective.
It increases the resolving power.
Parfocal
Stays in focus when switching between objectives
Parcentral
Object that’s centered will remain centered when switching between objectives
What does the condenser lens system do?
It focuses the light rays onto the specimen, producing a cone of light that illuminates the field evenly.
The condenser lens system is also sometimes called?
Sub-stage condenser
Mixing immersion oil types together may result in blurring
True or false?
True
In which type of microscope are specimens capable of bending light to appear as bright objects on a black field.?
Darkfield
What type of microscope has the following set up: 2 filters, one placed on top of the field diagram and the other between your eyes and the ocular, allowing visualization of components that are birefringent..
Polarizing.
What type of microscope uses the following principle: Specimen is illuminated using a specific short wavelength of light that is absorbed, and a longer wavelength is emitted to allow use to visualize.
Fluorescents
What type of microscope is very expensive and provides the highest magnification of any other microscope?
Electron
What type of microscope has the objectives and the oculars located below the stage?
Inverted microscope
