Quiz 1 Flashcards
1
Q
What are the main theories that describe optical phenomena
A
EM, Geometric, physical, quantum
2
Q
What are Maxwell’s Laws what do they mean
A
Gauss’s Law (1. electric charges, 2.magnetism) Faraday’s Law of induction, Ampere’s law
Maxwell’s equations describe how electric and magnetic fields are generated by charges, currents, and changes of the fields.Therefore, they describe how light is generated and how it propagates
3
Q
What is Lorentz Force and what does it do
A
Force exerted on a charged particle moving in an electric and magnetic field, (includes electric and magnetic component), responsible for many phen. -> binding of e- in nuclei and intermolecular interactions
4
Q
Gauss’s law of electric charges
A
electric fields are generated by single charges and diverge
5
Q
Gauss’s law of magnetism
A
no “magnetic charge”; magnetic fields are generated by dipoles and not originate in a single point
6
Q
Faraday’s law of induction
A
a spacially varying electric field is accompanied by a temporary varying magnetic field
7
Q
Ampere’s law
A
magnetic fields can be generated in two ways: by elec currents and/or by changing electric fields
8
Q
permeability
A
ability to support magnetic fields
9
Q
permittivity
A
the capacitance (the ability of a system to store an electric charge) that is encountered when forming a electric field in a medium
10
Q
Properties of light
A
- Carries electric and magnetic field, interaction with electric charges
- Frequency, wavelength, energy
- Momentum
- Polarization
- Coherence
- Interact with gravity
- Photon-photon interactions
- Obey bose-einstein statistics (photons = bosons (subatomic particle whose spin quantum number has an integer value), more than one photon can occupy a given state)
11
Q
What does an EM wave consist of
A
rapidly varying electric and magnetic fields which propagate through space
Energy from light can only be imparted to objects in discrete units called PHOTONS
The amount of energy that a photon can impart is proportional to its frequency
12
Q
Black body radiation
A
radiation emitted by all bodies due to temperature greater than 0 K
13
Q
What makes lasers different than normal light sources?
A
Coherent light (in phase/ same phase dif), same wavelength (monochromatic), more E dep freq, polarized, directional
14
Q
What are the main applications of lasers?
A
LASIK, printers, tattoo removal, laser pointer, Communications,
cutting materials, barcode
scanners
15
Q
What are the main thermal effects that lead to energy loss
A
Convection, conduction, radiation
16
Q
Novel dev in laser tech
A
miniaturization
17
Q
Radiative decay
A
relaxation of excited state to the ground state with emission of radiation (EM radiation, photons)
18
Q
How can light be emitted (3)
A
Heat sources. (fusion/combustion), luminescence (no heat), radioactivity
19
Q
Chemiluminescence
A
Describes the emission of light that occurs from chemical reactions
that produce high amounts of energy lost in the form of photons.
20
Q
Bioluminescence
A
Type of chemi-> Bioluminescent reactions are ATP-driven, and relate to a
certain molecule called Luciferin
21
Q
Luminescence
A
no heat light emission (chemiluminescence -> bio + photoluminescence -> fluo and phosph)
22
Q
Fluorescence + parameters
A
emission of light from an excited state created by absorption of light
Parameters: quantum yield, spectrum, lifetime, stokes shift
23
Q
Rayleigh scattering
A
Elastic scattering on molecules/objects smaller than incident
wavelength
24
Q
Mie scattering
A
Elastic scattering on molecules/objects similar to or larger than the
incident wavelength
25
Raman scattering
Inelastic scattering of photons by
matter, meaning that there is both
an exchange of energy and change
in the light’s direction
■ Inelastic: scattered photons have
different energy (usually lower) than
incident photons
26
Evolutionnary pressures for bioluminescence
1. Survival
a. Counterillumination camouflage, mimicry of other animals, for
example to lure prey or escape predators.
2. Reproduction
a. Signaling to other individuals of the same species to attract mates
27
Applications of Chemiluminescence:
● Glowsticks
● Forensics
● Protein blotting
● Immunoassay
○ Detection and assay of biomolecules in systems such as ELISA
● Pharmacological
● Toxicological testing
28
Photoelectric effect
The emission of electrons when electromagnetic radiation, such as light, hits a material. Electrons emitted in this manner are called photoelectrons.
Photoemission can occur from any material, but it is most common in
metals and other conductors.
29
What is the difference
between chemiluminescence,
fluorescence, and
phosphorescence?
Fluorescence and Phosphorescence are based on ability of substance to
absorb light and emit light of a longer wavelength and lower energy. The
difference between these two is that phosphorescence lingers for a longer
period of time.
Chemiluminescence needs activation for chemical reaction (requires ATP in
the bioluminescent case)
30
Huygens principle
When light interacts with a material at
an interface, points of interaction will
be sources for new spherical waves.
These waves will then interact with
each other, creating a wave front
31
Fermat principle
Fermat’s Principle: Light travels between points along the path of shortest time, not the shortest
distance (bc refractive index changes speed)
32
Total internal reflection
complete reflection of a ray of light within a medium such as water or glass from the surrounding surfaces back into the medium. The phenomenon occurs if the angle of incidence is greater than a certain limiting angle, called the critical angle
33
Pinhole use
spatial filtering
*control of the amount of light entering the system
*control of the Numerical Aperture (NA) of the imaging system
*control of the aberrations
34
Brewster's angle
Brewster's angle is an angle of incidence at which light with a particular polarization is perfectly transmitted through a transparent dielectric surface, with no reflection
35
Types of light manipulation optical components
pinholes, irises
*mirrors
*beam splitters
*filters
*lenses (build a telescope with a certain magnification)
*prisms
*gratings
*polarizers
*wave plates
*fibers
36
Types of filtres
*neutral density (ND) overall
*bandpass -> some part spectrum
*edge (long- or short-pass) -> long vs short wavelengths
*dichroic -> reflect color
*notch -> narrow bandpass
*diffusers -> softens light by scattering
37
What is optical grating
diffraction grating is an optical
element that disperses light
composed of lots of different
wavelengths(e.g., white light)
into light components by
wavelength.
38
What are metallic mirrors
Silver/alu mirrors which determine percentage of light of given wavelength that is reflected
39
What are dielectric mirrors
mirrors made of layered materials which create interference (reflect a lot of a specific wavelength)
40
What are prisms/uses
A prism works because the
different colors of light travel
at different speeds inside the
glass. They get bent by
different amounts and spread
out as they leave the prism.
● Used in spectrometers to
analyze spectral components
of light
41
What is the pinhole effect
an optical concept which suggests that the smaller the pupil size, the less
defocus from spherical aberrations are present (only focused, clear images are seen)
42
lenses types
biconvexe, plano convexe, positive meniscus, neg meniscus, plano concave, biconcave, fresnel, axicon, grin
43
Lens Sign Conventions
●Focal length is + if lens is double convex (converging)
●Focal length is – if lens is double concave (diverging)
●Image distance is + if the image is real and located on the other side of the
lens
●Image distance is – if the image is virtual and located on the object’s side
of lens
●Image height is + if the image is upright (and therefore virtual)
●Image height is – if the image is inverted (and therefore real)
44
Most common lenses
○ Double convex lenses, which are converging lenses that focus light
(image can be located on either side
of the lense, Virtual image can be upright or flipped, bigger or smaller)
○ Double concave lenses, which are diverging lenses that scatter light
(Image is located on object’s side of lense, virtual image for all (upright and reduced in size)
45
Cephalopod Camouflage:
Contains three types of cells:
○ Chromatophores: these contain elastic
sacs of pigment, whose expansion and
contraction is controlled by muscles.
When the sac is expended, the colour
within it is more visible
○ Iridophores: stacks of cells that reflect
light at different wavelengths and
polarities
○ Leucophores: scatter the full spectrum of
light, allowing them to appear white
46
Advantages and disadvantages of artificial photosynthesis
Advantages:
● Solar energy can be immediately converted and stored. In photovoltaic
cells, sunlight is converted into electricity and then converted again into
chemical energy for storage, with energy loss occurring with the second
conversion.
● The byproducts of APS are carbon-neutral
Disadvantages:
● Materials used for APS often corrode in water, may be less stable
● The cost is not advantageous enough to compete with fossil fuels as a
commercially viable source of energy
47
Differences between light and dark cycle photosynthesis
Light reactions:
● Occur in light
● Reactants: H2O
● Products: ATP, NADPH
● Used to convert light energy to chemical energy (ATP, NADPH) for the
Calvin Benson cycle
Dark reactions (Calvin Benson Cycle):
● Occur without light
● Reactants: CO2, ATP, and NADPH
● Products: Sugars
● Used to create sugars using the chemical energy made in the light
reactions
48
Numerical aperture
dimensionless number which
shows the range of angles over which a system can accept or emit light.
49
Types of light interactions
Reflection, refraction, absorption, emission, scattering, interference
50
Mean free path
The average distance over which a
moving particle travels before changing
its direction or energy (bc collisions with other particles)
Bigger = deeper imaging
Depends on n variations,
Size of scatterer, Wavelength (longer wavelength = bigger mfp)
51
Transmittance
the measure of how much light from a light source is able to pass through a material to the other side.
52
What eye structure is responsible for color vision
evenly distributed cones in the retina
53
photoisomerization
When light is absorbed by retinal it transforms into an activated version of itself (light triggers change in photoreceptor molecular comfirmation)
54
Phototransduction
process by which light detected by photoreceptor cells is converted to electrical impulses before these impulses are then sent to the brain.
result of memebrane depolarization + membrane proteins
55
Types of photoreceptor cells in the eye
Rod photoreceptor cells handle light intensity detection
Cone photoreceptor cells handle colour vision
56
Opsins
light-sensitive proteins found in photoreceptor cells -> eg retinol responsible for light absorption
57
Types of intramolecular forces
Ionic, covalent + metallic
58
Types of intermolecular forces
Van der Waals (dip-dip -> H-bonding, dip induced dip, london dispersion)
59
What is self-assembly
process in which a disordered system of pre-existing components forms an organized structure or pattern as a consequence of specific, local interactions among the components themselves, without external direction; i.e. spontaneously
60
Cohesion vs adhesion
Capillary action occurs due to forces of cohesion (attractions within the molecules of the liquid) and adhesion (attractions between the molecules of the liquid and the surface)
61
Lennard-Jones potential
Lennard-Jones potential describes the potential energy of interaction between two non-bonding atoms or molecules based on their distance of separation
consists of two parts: a steep repulsive term, and smoother attractive term, representing the London dispersion forces
sigma is the distance at which the intermolecular potential between the two particles is zero, and r is the distance of separation between both particles (from center)
62
Factors affecting photosynthetic rate
Light intensity, water, temperature
63
What are the necessary characteristics of renewable energy solutions
Distributed, available to all, low capex (simple enough engineering)
64
Cephalopod Camouflage
● Contains three types of cells:
○ Chromatophores: these contain elastic
sacs of pigment, whose expansion and
contraction is controlled by muscles.
When the sac is expended, the colour
within it is more visible
○ Iridophores: stacks of cells that reflect
light at different wavelengths and
polarities
○ Leucophores: scatter the full spectrum of
light, allowing them to appear white
65
Forces that drive self-assembly
Intra- and inter-molecular forces (mostly electrostatic in nature such as hydrogen bonds)
External forces such as electric and/or magnetic forces, flow, osmotic, gravitational
Combination of forces
Forces at interfaces (electrostatic or entropic) Other forces...
66
What are superhydrophobic affects due to
The presence of micro and nano (hierarchical) structured patterns on a surface
67
What is coffee ring effect and what is it useful for
Due to convection flow, particles from the center of the droplet move to the edges as particles from the edges are more rapidly evaporated. Surface tension is stronger than internal forces, so the surface stay the same longer than the distribution of particles inside the droplet.
This can be used to concentrate or separate particles
68
Concepts in complex systems (terms)
Modules/nodes: Integrated units that can be combined in many ways
Networks: systems of connected nodes
Topology: way nodes are organized (hierarchical, scale-free*, Distributed)
Robustness: ability of system to produce same output despite external changes
69
Hydrophobic regimes
Solid,
wenzel: Characterized by micro-structures into which the water
droplet embeds itself
cassie-baxter: Characterized by hierarchical nanostructures that the
water droplet “floats” above
70
Types of ion channels in membrane
Resting K+ channel, voltage-sensitve, ligand-gated (neurotransmitter), mechanical, signal-gated (intracellular molecule)
71
What can ion channels be used for
● Action potential: Voltage-sensitive channels in neurons and open and close in response to the voltage across the membrane.
● Neurotransmitters: Ligand-gated channels open and close in response to the binding of a ligand molecule.
● Sensory Neurons: Ion channels open and close in response to other stimuli, such as light, temperature or pressure.
72
Membrane potential
electrochemical gradient caused by charged or polar molecules (-72 mV)
73
Nerst potential
In a biological membrane, the reversal potential of an ion is the
membrane potential at which there is no net flow of that particular ion
from one side of the membrane to the other
74
Doping
Introducing impurities to the intrinsic (pure) lattice structure (i.e.,
semiconductor group IV element) can change its electrical properties.
n-type group V materials such as arsenic or phosphorus are added in
small quantities (5 valence electrons_ one free electron can move across the lattice, creating electric current.
p-type group III materials such as boron or gallium are added.
3 valence electrons, one free hole after bonding with Si. This hole can move
across the lattice, creating electric current.
increases the conductivity of the semiconductors!
75
Patch clamp technique
The dynamics of the ion channel can be studied using the patch clamp technique. This technique involves a glass micropipette which forms a tight gigaohm seal with the cell membrane. The micropipette contains a wire bathed in an electrolytic solution to conduct ions. To measure single ion channels, a “patch” of
membrane is pulled away from the cell after forming a gigaohm seal.
76
Electrodiagnosis types
Electrocardiography
Electroencephalography (synchronized signals)
Electromyography. (muscles and muscle nerve cells)
77
Connexons
connexon, also known as a connexin hemichannel is an assembly of six proteins called connexins that form the pore for a gap junction between the cytoplasm of two adjacent cells. This channel allows for bidirectional flow of ions and signaling molecules. (faster transmission without neurotransmitters)
78
Saltatory conduction
Schwann cells myelinate axons, potential can only travel at nodes of ranvier so appears to skip the myelinated regions on the axon
79
Action potential
Depolarization (na come out), repolarization (K come out too), hyperpolarization (K come out a lot) and refractory period (pump Na. out K in)
