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Microscopy
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Untitled Deck
Study
1
Question
What are the different types of light sources used in light microscopy?
Answer
Light microscopy uses natural sunlight, artificial light sources like incandescent light bulbs, low voltage lamps, halogen lamps, LEDs, high pressure gas discharge lamps, and lasers.
2
Question
What are the characteristics of coherent light?
Answer
Coherent light is light that has the same wavelength, direction of propagation, and no phase shift. It can be coherent in both time and space.
3
Question
What is polarization?
Answer
Polarization refers to the orientation of the oscillation plane of light. Linear polarized light has only one oscillation plane, while circular polarized light rotates at a steady rate in a plane perpendicular to the direction of the wave.
4
Question
What are the advantages of low voltage lamps?
Answer
Low voltage lamps have low power consumption, high luminance, are dimmable, provide a white light source, have a long lifetime, and are suitable for various microscopy techniques including brightfield, polarization, phase contrast, and fluorescence microscopy.
5
Question
What are high pressure gas discharge lamps and how do they work?
Answer
High pressure gas discharge lamps, such as mercury-vapor lamps and xenon arc lamps, generate light through a gas discharge between two electrodes. The excitation energy of the gas filling is emitted as characteristic radiation. They have a burning voltage of only 20 V.
6
Question
What is the difference between mercury-vapor lamps and high pressure gas discharge lamps?
Answer
Mercury-vapor lamps emit characteristic radiation in the shortwave range, while high pressure gas discharge lamps have a broad range emission.
7
Question
What are the advantages and limitations of high pressure gas discharge lamps?
Answer
Advantages: They have longer lifetimes compared to low voltage lamps and provide higher intensities. Limitations: They have high heat dissipation, limited lifetime, and often result in nonuniform illumination of the image field.
8
Question
What are the characteristics of metal halide arc lamps?
Answer
Metal halide arc lamps have widened bands and higher intensities between the bands compared to high-pressure mercury-vapor lamps. They have a longer lifetime of approximately 2000 hours.
9
Question
What are light-emitting diodes (LEDs) and how do they work?
Answer
LEDs are light sources made of semiconductor material. They convert electric current directly into light through the process of recombination. When electrons collide with holes, energy is emitted in the form of light.
10
Question
What are the advantages of LED light sources?
Answer
LED light sources have a long lifetime, high stability, emit light in different wavelength ranges, generate minimal heat, and have low energy consumption.
11
Question
What are some applications of LED light sources in microscopy?
Answer
LED light sources are widely used in brightfield and fluorescence microscopy.
12
Question
From the p-side to the n-side
Answer
The movement of the holes (positive charges) from the p-side to the n-side.
13
Question
From the n-side to the p-side
Answer
The movement of the electrons from the n-side to the p-side.
14
Question
Current flow
Answer
The flow of electric current through a diode when it is forward biased.
15
Question
No current flow
Answer
The absence of electric current flow through a diode when it is reverse biased or in equilibrium.
16
Question
Die angelegte Spannung verhindert die Diffusion der Ladungsträger durch den Übergangsbereich
Answer
The applied voltage prevents diffusion of charge carriers through the transition region.
17
Question
Electrons
Answer
Negatively charged particles in an atom that move through a conductor.
18
Question
Löcher (holes)
Answer
Positively charged vacancies in the electron structure of an atom that move through a semiconductor.
19
Question
Tipler/Mosca Physik (Spektrum Akademischer Verlag, 6. Aufl., 2009)
Answer
A physics textbook discussing the principles of diodes and LEDs.
20
Question
In general functional principle of diodes
Answer
Diodes allow the flow of electric current in one direction and prevent it in the opposite direction.
21
Question
LED (Light-Emitting Diode) light sources
Answer
Semiconductor devices that convert electric current directly into light.
22
Question
Forward bias
Answer
The application of a voltage that promotes the diffusion of holes from the p-side to the n-side and electrons from the n-side to the p-side, allowing current flow.
23
Question
Reverse bias
Answer
The application of a voltage that prevents the diffusion of charge carriers through the transition area, resulting in no current flow.
24
Question
Semiconductor compounds
Answer
Materials that have the ability to conduct electric current under certain conditions.
25
Question
LED advantages
Answer
- Long life time - High stability - Many different wavelength ranges - No significant heat generation - Low energy consumption
26
Question
Applications of LED light sources
Answer
- Bright field microscopy - Fluorescence microscopy - White LED: blue LED with phosphorus layer
27
Question
Absorption of energy causes elevation of an electron to a higher energy level
Answer
The absorption of energy by an electron in an atom causes it to move to a higher energy level.
28
Question
Spontaneous emission of energy
Answer
When an electron in an excited state falls back to the ground state, it emits a photon of energy.
29
Question
Light amplification by stimulated emission of radiation
Answer
When an electron in an excited state is stimulated by a photon, it falls back to the ground state and emits a photon, resulting in light amplification.
30
Question
Gas lasers
Answer
Laser systems that use gas-filled tubes as the gain medium.
Untitled Deck
Study
1
Question
Microscope
Answer
A device used to magnify small objects that cannot be seen with the naked eye.
2
Question
Retina
Answer
The layer of cells at the back of the eye that converts light into electrical signals for the brain to process.
3
Question
Resolution
Answer
The ability to distinguish and separate details in an image.
4
Question
Accommodation
Answer
The ability of the eye to adjust its focus for objects at different distances.
5
Question
Refraction
Answer
The bending of light as it passes from one medium to another.
6
Question
Refractive Index
Answer
A measure of how much a medium can bend light.
7
Question
Snell's Law
Answer
A law that describes the relationship between the angles of incidence and refraction when light passes from one medium to another.
8
Question
Optical Glass
Answer
A type of glass with specific optical properties used for making lenses and optical systems.
9
Question
Quartz Glass
Answer
A type of glass made of pure SiO2 with high transparency in the UV and IR regions of the spectrum.
10
Question
Crown Glass
Answer
A type of glass with a high content of K, Na, or Ca oxide, commonly used for lenses.
11
Question
Flint Glass
Answer
A type of glass with a high content of Pb oxide, known for its high refractive index and dispersion.
12
Question
Quartz Lens
Answer
A lens made of quartz glass, known for its high transparency and low dispersion properties.
13
Question
Fluorite Lens
Answer
A lens made of CaF2 crystals, highly transparent in the UV and IR regions and with low dispersion.
14
Question
Glass
Answer
A non-crystalline, amorphous solid with optical properties that can vary depending on its composition.
15
Question
Light Dispersion
Answer
The separation of white light into its component colors due to the different refractive indices of the colors.
16
Question
What is the collecting lens?
Answer
The collecting lens is a lens used in microscopy to gather and focus light onto the specimen.
17
Question
What is the function of the collecting lens?
Answer
The collecting lens collects light from the light source and focuses it onto the specimen, improving illumination.
18
Question
What is the shape of the collecting lens?
Answer
The collecting lens is usually convex in shape, with a curved surface that bulges outward.
19
Question
Why is the collecting lens convex in shape?
Answer
The convex shape of the collecting lens helps in converging the light rays and focusing them onto the specimen.
20
Question
What is the position of the collecting lens in a microscope?
Answer
The collecting lens is located between the light source and the condenser lens.
21
Question
What is the role of the collecting lens in a microscope?
Answer
The collecting lens collects and concentrates the light from the light source, enhancing the quality and intensity of the illumination.
22
Question
What is the numerical aperture of the collecting lens?
Answer
The numerical aperture of the collecting lens determines the light-gathering ability and resolution of the microscope system.
23
Question
How does the collecting lens affect the brightness of the microscope image?
Answer
The collecting lens increases the brightness of the microscope image by gathering and focusing more light onto the specimen.
24
Question
What are some common materials used for making collecting lenses?
Answer
Some common materials used for making collecting lenses include glass, plastic, and quartz.
25
Question
What is the difference between the collecting lens and the condenser lens?
Answer
The collecting lens gathers and focuses light onto the specimen, while the condenser lens focuses light onto the objective lens.
26
Question
What happens if there is no collecting lens in a microscope?
Answer
Without a collecting lens, the illumination of the specimen would be poor, resulting in a darker and less detailed image.
27
Question
What is the purpose of using a collecting lens with a high numerical aperture?
Answer
A collecting lens with a high numerical aperture can gather more light and provide better resolution, resulting in clearer and more detailed images.
28
Question
How does the position of the collecting lens affect the illumination of the specimen?
Answer
The position of the collecting lens determines how much light is collected and focused onto the specimen, affecting the overall illumination.
29
Question
What is the relationship between the collecting lens and the objective lens?
Answer
The collecting lens gathers and focuses light onto the specimen, while the objective lens magnifies and resolves the details of the specimen.
30
Question
What are some factors to consider when selecting a collecting lens?
Answer
Some factors to consider when selecting a collecting lens include the required numerical aperture, working distance, and material compatibility.