Exam 1 Flashcards
Robert Hook
used compound microscope in 1665 to observe “cells” from cork
Define Cone Cells
the eye receptors of the retina used for sensing color
Define Rod Cells
cells distinguishing levels of intensity
What is the basic set up of a microscope?
light
lends
source
detector
List the forms of electromagnetic radiation in order of increasing wavelength.
Gamma Rays X-rays Ultraviolet Visible - R.O.Y.G.B.I.V. Infrared Microwaves Radio -AM -FM
Why do biologists primarily use infrared?
use it for biological tissue because of less scattering and deep penetration
Define Transparency
allows objects to be seen clearly through it
Define Opacity
the condition of lacking transparency
What are the properties of light?
wave
-periodic osillation that transmit energy through space
-3 parts; wavelength, amplitude, frequency
particle
True or False
All objects emit electromagnetic radiation.
True
UV Catastrophe
based on wave theory of light, classical physics predicts that energy increases as wavelength decreases (continuous relationship)
it is not a continuous relationship (bell-curve)
What two components are always perpendicular to each other in electromagnetic radiation?
electrical and magnetic
Name the three problems to overcome to improve resolution
Chromatic Aberration
Spherical Aberration
Lack of Light
Chromatic Aberration
- unequal bending of different wavelengths of light
- creates bluish halo
Spherical Aberration
light rays that pass through different parts of lens (center vs periphery) focus to different points
Name the types of lens
convex
plano-convex
concave
plano-concave
Achromatic Doublet Lens
-look like plano-concave
designed to eliminate chromatic and spherical aberrations inherent in singlet lenses
Black-Body Radiation
- an opaque and non-reflective body that is in thermodynamic equilibrium with its surroundings
- an E.M. radiation given off by a this emitter
- at room temperature, the object emits most of its energy as I.R. and absorbs all visible light thus appearing black
ex) planets and stars
Stefan-Boltzmann Law
relates total energy emitted is directly proportional to the 4th power of temperature
If two waves with the same frequency and speed are present, the wave with the higher or lower amplitude has greater energy?
higher
Abbe’s Theory of Image Formation
Condenser Iris
Condenser Lens
Specimen
Objective Lens
Objective Rear Focal Plane (diffraction on pattern)
-this part determines the specimen using diffraction pattern
(if I don’t get all of the diffraction pattern, I don’t get the entire image)
Numerical Aperature
- NA
- measures of light bending by the material
True or False
Higher NA = Shorter Working Distance
True
What is the difference between Ernest Abbe’s and Sir Raleigh’s limits of resolution equations?
Sir Raleigh’s equations takes into account contributions due to diffraction
True or False
Higher NA Objective = Worse Resolution
False
Point Spread Function
- P.S.F
- describes the optical systems response to a point source
True or False
Resolution depends on the NA and wavelength of light
True
True or False
As wavelength gets longer (blue to red) resolution will become better
False
Frank - Condon Principle
Electric distribution changes occur more rapidly compared to bond angles and distances
Bathochromic Shift
The more conjugation a molecule has, the more it leads to increased shift to longer wavelengths for absorption
Why is there a difference of broading peaks between a gas and a solution?
- gases produce sharp absorption and emission bands because of the space between molecules
- molecules in solution do not produce sharp absorption/emission bands due to electronic, vibrational and rotational bonds transitions (more molecules to interact with
True or False
Most fluorescence molecules are aromatic
True
Name 3 Optical Instruments
camera binocular telescope spectrophotometer spectrofluorimeter microscope
Name 3 Critical Components of Optical Instruments
light sources optical filters monochrometors polarizers lens detectors
Name 3 Light Sources
sunlight candles gas flame Tungsten-Halogen Lamp Xenon Arc Lamp Lasers LEDs
Tungsten-Halogen Lamp
- used due to high melting point
- poor emission efficiency (wavelength dependent) (as wavelength increases, molar absorbing decreases)
Arc Lamp
- 10 to 100x brighter than Tungsten-Halogen Lamp
- shorter lifespan
Name the three types of instability of Arc Lamps
arc wander
arc flare
arc flutter
LASERS
- light amplification by stimulated emission of radiation
- electrons are brought to excited state triggering a chain reaction
LEDs
- long operating lifetimes
- excellent temporal and spatial stability
- lowest operating temperatures due to fully reversible photoelectric effect
What does brightness of image depend on?
depends on source of brightness and magnification
What are the three types of Optical Filters?
- band pass (allow only a limited number of wavelength of light to pass)
- long pass (only allow wavelength of light longer than the specificed cutoff to pass)
- neutral density (not specific to wavelength rather used to adjust the intensity or brightness of a light source used for imaging)
Monochromator
- diffract light (separate visible wavelengths)
Polarized Light
- a light where a component of the E.M. radiation is blocked
Birefigent Materials
- materials whose refractive index depends on the polarization and propagation of light
- aka a double refraction created from the material
Name 3 types of Detectors
- human eye
- photomultipler Tube (PMT)
- avalanche photodiode (APD)
- charged coupled device (CCD)
