Lecture 1 Flashcards
Lorentz force equation
F = qE +qb*B
Gauss’s law
electric fields are generated by single charges and diverge
Gauss’s law (magnetism)
No magnetic charge magnetic fields are generated by dipoles and not originate in a single point
Faraday’s law of induction
a spatially varying electric field is accompanied by a temporary varrying magnetic field
Ampere’s law
magnetic fields can be generated in two ways: by electric currents and changing electric fields
permeability
the ability of a medium to support magnetic fields
permittivity
the capactance encountered when forming an electric field in a medium. In other words, the energy-storage capacity of the field in the medium
descibe the properties of light
light is an electromagnetic wave, carries electric and magnetic fields, allowing it to interact with electric charges
describ light waves
light waves have a frequency, a wavelength, a certain energy, as well as given momentum.
Light equations
c=入V
E=hv=hc/入
p=E/c
light properties
Light can also have a polarization, that is, the wave might oscillate in a specific plane of
the electric field. If you have polarized sunglasses, you can try holding them up to your
computer screen and then rotating them 90 degrees while keeping your head upright!
light properties
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
Light is also a particle! Photons have mass, and, as such, light will interact with gravity.
Photons can also interact with each other.
Photons are categorized as
Photons are categorized as “bosons”: more than one photon can occupy a given state.
This means light obeys Bose-Einstein statistics.
All objects emit radiation(light)
All objects emit radiation (light) due to accelerated charges at T>0K; thermal radiation (black body radiation)
Stephan-Boltzman law
P = SigmaAT^4
sigma = (2pi^5k^4)/(15c^2h^3) = 5.670373*10^-8 WM^-2K^-4
heat transfer can be calculated
Pnet = Pemit - Pabsorb
Pnet = AsigmaE(T^4-T0^4)
light emiited from higher energy level to lower energy level
E2-E1 = delta E = hv
Lasers differ from other light sources for a few reasons
They operate using a single wavelength, and, as such, are monochromatic.
* They are coherent.
* They are directional. This means the light is spatially targeted, the light barely
diverges. This contrasts with flashlights, for example.
* They are polarized.
Lasers come in two varieties, continuum wave (CW) and pulsed
Continuum wave lasers operate at a constant output power with no
interruptions in the beam of light.
* Pulsed lasers 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.
Lasers have many practical applications
Optical tweezers
* Medical purposes (eg.: LASIK)
* Motion detection
* Mass spectroscopy
* Scanning
* DNA sequencing
