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What are the different types of light sources used in light microscopy?
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.
What are the characteristics of coherent light?
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.
What is polarization?
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.
What are the advantages of low voltage lamps?
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.
What are high pressure gas discharge lamps and how do they work?
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.
What is the difference between mercury-vapor lamps and high pressure gas discharge lamps?
Mercury-vapor lamps emit characteristic radiation in the shortwave range, while high pressure gas discharge lamps have a broad range emission.
What are the advantages and limitations of high pressure gas discharge lamps?
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.
What are the characteristics of metal halide arc lamps?
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.
What are light-emitting diodes (LEDs) and how do they work?
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.
What are the advantages of LED light sources?
LED light sources have a long lifetime, high stability, emit light in different wavelength ranges, generate minimal heat, and have low energy consumption.
What are some applications of LED light sources in microscopy?
LED light sources are widely used in brightfield and fluorescence microscopy.
From the p-side to the n-side
The movement of the holes (positive charges) from the p-side to the n-side.
From the n-side to the p-side
The movement of the electrons from the n-side to the p-side.
Current flow
The flow of electric current through a diode when it is forward biased.
No current flow
The absence of electric current flow through a diode when it is reverse biased or in equilibrium.
Die angelegte Spannung verhindert die Diffusion der Ladungsträger durch den Übergangsbereich
The applied voltage prevents diffusion of charge carriers through the transition region.
Electrons
Negatively charged particles in an atom that move through a conductor.
Löcher (holes)
Positively charged vacancies in the electron structure of an atom that move through a semiconductor.
Tipler/Mosca Physik (Spektrum Akademischer Verlag, 6. Aufl., 2009)
A physics textbook discussing the principles of diodes and LEDs.
In general functional principle of diodes
Diodes allow the flow of electric current in one direction and prevent it in the opposite direction.
LED (Light-Emitting Diode) light sources
Semiconductor devices that convert electric current directly into light.
Forward bias
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.
Reverse bias
The application of a voltage that prevents the diffusion of charge carriers through the transition area, resulting in no current flow.
Semiconductor compounds
Materials that have the ability to conduct electric current under certain conditions.
LED advantages
- Long life time - High stability - Many different wavelength ranges - No significant heat generation - Low energy consumption
Applications of LED light sources
- Bright field microscopy - Fluorescence microscopy - White LED: blue LED with phosphorus layer
Absorption of energy causes elevation of an electron to a higher energy level
The absorption of energy by an electron in an atom causes it to move to a higher energy level.
Spontaneous emission of energy
When an electron in an excited state falls back to the ground state, it emits a photon of energy.
Light amplification by stimulated emission of radiation
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.
Gas lasers
Laser systems that use gas-filled tubes as the gain medium.
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Microscope
A device used to magnify small objects that cannot be seen with the naked eye.
Retina
The layer of cells at the back of the eye that converts light into electrical signals for the brain to process.
Resolution
The ability to distinguish and separate details in an image.
Accommodation
The ability of the eye to adjust its focus for objects at different distances.
Refraction
The bending of light as it passes from one medium to another.
Refractive Index
A measure of how much a medium can bend light.
Snell's Law
A law that describes the relationship between the angles of incidence and refraction when light passes from one medium to another.
Optical Glass
A type of glass with specific optical properties used for making lenses and optical systems.
Quartz Glass
A type of glass made of pure SiO2 with high transparency in the UV and IR regions of the spectrum.
Crown Glass
A type of glass with a high content of K, Na, or Ca oxide, commonly used for lenses.
Flint Glass
A type of glass with a high content of Pb oxide, known for its high refractive index and dispersion.
Quartz Lens
A lens made of quartz glass, known for its high transparency and low dispersion properties.
Fluorite Lens
A lens made of CaF2 crystals, highly transparent in the UV and IR regions and with low dispersion.
Glass
A non-crystalline, amorphous solid with optical properties that can vary depending on its composition.
Light Dispersion
The separation of white light into its component colors due to the different refractive indices of the colors.
What is the collecting lens?
The collecting lens is a lens used in microscopy to gather and focus light onto the specimen.
What is the function of the collecting lens?
The collecting lens collects light from the light source and focuses it onto the specimen, improving illumination.
What is the shape of the collecting lens?
The collecting lens is usually convex in shape, with a curved surface that bulges outward.
Why is the collecting lens convex in shape?
The convex shape of the collecting lens helps in converging the light rays and focusing them onto the specimen.
What is the position of the collecting lens in a microscope?
The collecting lens is located between the light source and the condenser lens.
What is the role of the collecting lens in a microscope?
The collecting lens collects and concentrates the light from the light source, enhancing the quality and intensity of the illumination.
What is the numerical aperture of the collecting lens?
The numerical aperture of the collecting lens determines the light-gathering ability and resolution of the microscope system.
How does the collecting lens affect the brightness of the microscope image?
The collecting lens increases the brightness of the microscope image by gathering and focusing more light onto the specimen.
What are some common materials used for making collecting lenses?
Some common materials used for making collecting lenses include glass, plastic, and quartz.
What is the difference between the collecting lens and the condenser lens?
The collecting lens gathers and focuses light onto the specimen, while the condenser lens focuses light onto the objective lens.
What happens if there is no collecting lens in a microscope?
Without a collecting lens, the illumination of the specimen would be poor, resulting in a darker and less detailed image.
What is the purpose of using a collecting lens with a high numerical aperture?
A collecting lens with a high numerical aperture can gather more light and provide better resolution, resulting in clearer and more detailed images.
How does the position of the collecting lens affect the illumination of the specimen?
The position of the collecting lens determines how much light is collected and focused onto the specimen, affecting the overall illumination.
What is the relationship between the collecting lens and the objective lens?
The collecting lens gathers and focuses light onto the specimen, while the objective lens magnifies and resolves the details of the specimen.
What are some factors to consider when selecting a collecting lens?
Some factors to consider when selecting a collecting lens include the required numerical aperture, working distance, and material compatibility.
