Quiz 1 Flashcards
What are the properties of light?
1) light carries electric and magnetic fields
2) Light has a frequency, wavelength, momentum and carries energy
3) Light can have a polarization
4) Light has coherence meaning it can be in or out of phase for constructive or destructive interference
5) Light is a particle. Photons can interact with other photons, gravity and have mass
6) Photons are bosons meaning more than one photon can occupy a given state
What formulas specify energy, momentum and wavelength of light?
What is the classical electromagnetic theory? What formula does it represent?
The classical electromagnetic theory is represented by the Lorentz force, which is the force of a particle moving through an electromagnetic field.
What is Gauss’s law of electric charges?
Describes the generation of an electric field by a single charge.
What is Gauss’s law of magnetism?
Describes the generation of a magnetic field by magnetic dipoles. No single-point charges.
What is Faraday’s law?
Describes how a moving electric field can generate a magnetic field.
What is ampere’s law?
Describes the creation of a magnetic field by electric currents and/or moving electric fields.
How can classical electromagnetic theory describe light?
It is one of four forces in nature (gravity, weak, EM, strong). Light is self-propagating because it is the composite of two waves varying in unison (electric and magnetic). There are two main acting forces in EM theory –> electrostatic forces and magnetic forces
What are ways light can be generated?
1) from a heat source such as thermal or radiation
2) from the emission spectrum of translucent matter interacting with a specific spectrum
What is black body radiation?
It is also known as thermal radiation and is emitted by all objects with temperatures above 0K.
How do you calculate net radiative heat loss?
What makes lasers different than normal light sources?
Laser light is directional, coherent, monochromatic and polarized.
What thermal effects may lead to energy loss?
Conduction, convection, radiation
How do you calculate the total energy radiated by a body?
E = (P)(t)
How is light generated?
When electrons are excited to a higher energy level through a different process, when the electrons are excited and fall back to a relaxed state they release photons and light is produced.
What is stimulated decay?
This implies a catalyst incident photon triggers the emission of a second photon from an atom.
How do you calculate exponential decay?
What is mean lifetime and how is it calculated?
What is fluorescence?
It is a property in which a compound can absorb light of a specific wavelength and emits a different wavelength of light. Typically has a shorter mean lifetime or half-life.
What is phosphorescence?
It is similar to fluorescence; however, the material does not immediately re-emit the absorbed radiation. The transition from excited state to ground state happens much slower and the light re-emitted has a lower intensity.
What is photoluminescence?
It is the emission of light by the absorption of another photon. This process is known as stimulated emission!
What is chemiluminescence and how is it related to bioluminescence?
Chemiluminescence is the emission of light by a chemical reaction. Bioluminescence is a type of chemiluminescence as it involves the reaction in which ATP drives the oxidation of optical molecule luciferin with the help of enzyme luciferase to form oxyluciferin and light. The excited state of luciferin will emit of a photon.
How do you calculate the quantum yield?
What is Rayleigh scattering?
It is elastic scattering on objects with smaller wavelengths than the incident light.
What is Mie scattering? What calculations are associated with it?
It is also elastic scattering, however the objects are similar in size as the incident wavelength.
What is elastic scattering?
the interaction between the object and light does not involve any energy transfer.
What is raman scattering?
It is inelastic scattering which means there is an energy exchange when light is in contact with the object. This results in polarization change in the molecules being hit by light. The energy of the scattered photon does match that of the incident one.
What is the difference between chemiluminescence, fluorescence and phosphorescence?
Fluorescence and phosphorescence are similar in that they both absorb light of a specific wavelength and emit one with a different one. However, phosphorescence there is a delay in light emission the intensity is a lot.
On the other hand, chemiluminescence requires a chemical reaction (input of energy such as ATP) to produce light.
What is the main difference between bioluminescence and thermal radiation?
Bioluminescence generate light by a chemical reaction whereas thermal radiation generated by heat.
What evelutionary pressures drive bioluminescence?
Survival and reporduction
What is the photoelectric effect?
It is the emission of electrons when electromagnetic radiation such as light hits a material. These elctrons are called photoelectrons.
Recognize wave equations
Describe the huygens-fresnel principle
when light interacts with a material at an interface each point of interaction is a source from new spherical waves which creates a wave front.
What is fermat’s principle?
Light always travels the path of shortest time not distance.
Know snell’s law equation
What is total internal reflection? How do you calculate the critical angle?
It implies that there is no refraction of light because it is entering a medium that is less dense causing the incident beam to be completely reflected.
What is Brewster’s angle and how do you calculate it?
It occurs when the angle between the reflected and refracted rays are 90 degrees. The reflected rays will be polarized, and the refracted rays will only be partially polarized.
What are the purposes of pinholes and irises and what is the pinhole effect?
pinholes control the amount and plane of light passing through to the system. The pinhole effect suggests that the smaller the pupil size, the less defocus from spherical aberrations there are. This is because all unfocused rays are blocked leaving only focused light to land on the retinal and control a clear image.
What is the difference between dielectric mirrors and metallic mirrors?
dielectric mirrors have a thin layer of oil, water or air so that light can interfere with itself either constructively to destructively. Mettalix mirrors are made of silver and aluminium and the percentage
What are beam splitters?
They are used to divide an incident beam into two separate beams. One is reflected and the other is transmitted.
What do filters do? What types of filters are there? (hint: there are 6!)
Filters control the intensity of light and its spectral characteristics.
Neutral density filters = change the intensity of light, but not the wavelength.
Bandpass filters = only allow a specific range of wavelengths through (they let a specific band pass).
Edge filters = allow only long wavelength or short wavelength light to pass, depending on the type (long-pass or short-pass).
Dichroic filters = only allow a very small range of wavelengths to pass. They are similar to bandpass filters.
Notch filters (also referred to as bandstop filters) = let all wavelengths through except those within a specific range.
Diffusers = make the incoming beam of light less abrasive, less intense and more ambient overall. These are often used in photography studios, for example, to properly light a subject!
What do lenses do?
They convert planar waves into circular waves to focus light on a specific point or scatter light away from a specific point.
What is the lens maker’s equation (1)?
What is the lens maker’s equation (2)?
What do prisms do?
Made of at least two flat surfaces with a difference in angle. They disperse, split or reflect light into various polarizations or wavelengths. They work because different colours travel at different speeds.
What are gratings and how do they work?
It is an element that disperses light composed of different wavelengths into light components by wavelength. When white light enters a grating, the light components are diffracted at angles that are determined by respective wavelengths.
What equations are associated with gratings?
What is polarization?
It applies to transverse waves and specifies the geometrical orientation of the oscillations.
In a transverse wave the direction of oscillations is perpendicular to the direction of motion of the wave. In linear polarizations the fields oscillate in a single single direction.
How do optical fibers work? What formula represents the incident angle?
They operate by total internal reflection.
The internal material must have a larger index compared to the cladding (material that wraps glass)
What is the lens equation and magnification equation?
What is the lens makers equation?
What are compound lenses?
lens made of simple lenses mounted on a common axis usually in close juxtaposition.
Position 6 is at the focal point
● When an object is placed on the focal point, no images are produced (virtual or real)
● This is because the refracted rays neither converge or diverge
● After refracting, the light rays are travelling parallel to each other and cannot produce an image
What is beer-lambert’s law?
Describes the of which absorption occurs based on the material light is interaction with.
What is the formula for absorbance and scattering coefficients, what are they both defined by?
They are both defined by the cross-sectional area of the material which is interacting with light.
What is transmittance? How do we calculate it for both absorption and scattering?
It is the measure of how much light from a light source is able to pass through a material to the other side. How much light is not being scattered or absorbed.
How can we use the interaction with light and tissue as an engineer?
Q1: Why can’t we use light in the
visible range for deep tissue
penetration? Which wavelengths
of light can be used?
Describe the overall visual process:
What is coulomb’s law and what is the formula?
Quantifies the electrostatic force between charged particles.
What is coulomb’s law and what is the formula?
Quantifies the electrostatic force between charged particles.
Lenard Jones formula
What is spontaneous self-assembly and what formulas help explain it?
It is a spontaneous process that releases free energy.
G < 0 and there must be a gain in entropy S > 0
How do you quantify hydrophobicity?
What is wenzel regime and cassie-baxter regime?
Wenzel: micro-structures in which water droplets embed themselves in the spaces
Baxter: hierarchical nanostructures that water floats on
List the types of channel proteins a membrane can have
What are the properties of an electric circuit?
Draw the Hodgkin-Huxley circuit and equations for the current through the lipid bilayer, ion channel currents and total current.
Write out the nernst and goldman equation
Why is the membrane similar to N-P junctions
In the “N-doped” area, group 5 elements are added in small quantities. The single fifth electron will be mobile in the system. In the “P-doped” area, group 3 elements are added in small quantities. The “gap” left by the mission valence electron will lead to current generation when free electrons from the N-doped region migrate to the P-doped region. Overall, a junction potential is created, much like the potential generated in the case of the plasma membrane!
How are values for ion
concentration experimentally
obtained?
