Optics fundaments + Generation of light in biology Flashcards
What is classical electromagnetism?
The study of electrical charges and their motion
What are the main forces of nature
Gravitational force, weak nuclear force, electromagnetism force and strong nuclear force
What is the Lorentz force
The force exerted on a charged particle moving in an electric and magnetic field F=qE+qv x B
It is responsible for binding electrons to nuclei as well as intermolecular interactions.
Maxwell’s equations + laws
They describe the generation and propagation of light.
- Gauss’s law (electric charge): electric fields are generated by a single charge and diverge ∇.E= ρ/ε0
- Gauss’s law (magnetism): magnetic fields are generated by dipoles and do not originate from a single point ∇.B=0
- Faraday’s law of induction: Describes the creation of a temporary varying magnetic field by a moving electric field ∇xE= -dB/dt
- Ampere’s law: magnetic field can be generated in 2 ways: by electric currents and/or by changing electric fields ∇xB= µ0 J+µ0ε0 dE/dt
What does an electromagnetic wave consists of?
rapidly varying electric and magnetic fields which propagate through space
What is permeability?
the ability to support magnetic fields (how much fluid can pass through a membrane)
What is permittivity?
the capacitance that is encountered when forming an electric field in a medium (the ability of a material to store energy within it)
Properties of light (7)
- light, an electromagnetic wave, carries electric and magnetic fields allowing it to interact with electric charges
- light waves have a frequency/wavelength/energy and given momentum
c=λv
E=hv=hc/λ
p=E/c (momentum)
-light can have a polarization(the wave might oscillate in a specific plane of the electric field)
-As light is a wave, sets of these waves can be in or out of phase with each other. The
relationship between these phases is called coherence.
-Light is also a particle! Photons have mass, and, as such, light will interact with gravity.
-photon-photon interactions
-obey Bose-Einstein statistics (photons are bosons(particles that carry energy and forces throughout the universe), more than one photon can occupy a given state)
What are the thermal effects that can lead to energy loss?
convection,conduction,radiation
heat transfer by radiation equations (3)
- λ=b/T with b=2900 µm.K
- σ=5.67 x 10^-8 Wm^-2 K^-4
- Pnet=Pemit-Pabsorb=Aσε(T^4-To^4) with A=surface area and ε=emissivity 1
How do atoms emit light? What are the two types
Atoms emit light when their electrons are lowered to less energized states. The released
energy takes the form of light. the energy of the released photon is equal to E2-E1=hv
Types:
-natural
-stimulated-> a catalyst incident photon triggers the emission of a second photon
How do lasers differ from other light sources? What are the two types of lasers? What are their applications? What are the developments in laser technology
Lasers differ from other light sources for a few reasons:
- monochromatic. They operate using a single wavelength.
- They are coherent.
- They are directional. This means the light is spatially targeted, and the light barely
diverges.
- They are polarized.
Two types:
-Continuum wave: operates at a constant output power with no
interruptions in the beam of light
- Pulsed: operate at similar average power outputs to the CW laser but only emit light intermittently and for very short periods of time. As such, the power output per burst is much greater than that of CW lasers.
Applications:
Optical tweezers, medical purposes(LASIK), motion detection, mass spectroscopy, barcode scanners, cutting through materials, printing, and DNA sequencing,…
Development:
Miniaturization of lasers for smaller systems
What are the main ways in which light is generated and what are their sources?
Radiation (heat source)
Radioactivity (Gamma rays)
Luminescence (generated from a source other than heat)
Non-radioactive decay (no release of a photon, the material heats up)
What are the types of luminescence and their mechanism?
Photoluminescence (absorption of another photon)
Chemiluminescence(chemical reactions)
Electroluminescence(electric current)
Mechanoluminescence(mechanical stress)
What is the radiative/exponential decay ODE equation?
dN/dt= -λN –> solution N(t)= N0 e^(-λt)
