Khan Flashcards
Electromagnetism
This is one form of how energy radiates through space
Waves
These are disturbances within a medium or field which results in a vibration or oscillation
Electromagnetic waves
These have perpendicular electric and magnetic fields that oscillate like a wave. The moving charged particle induces a magnetic field and the changing magnetic field produces an electric field. Because the fields are coupled Maxwell positted that light must be a wave independent of the source.
Given that magnetism and electricity are not physical, massive things EMR goes through anything.
wavelength frequency relationship
C = λ v
where C = speed of light in a vaccum = 2.99 * 108 m/s
v = frequency (1/s = Hz)
λ = wavelength (m)
Gamma ray wavelength and frequency
λ = 10 ^ -17- -11
v = 10 ^ 19 - 25
This is the highest frequency EMR
x-ray wavelength and frequency
λ = 10 ^ -11- -8
v = 10 ^ 17 - 19
This is the second highest frequency EMR
UV wavelength and frequency
λ = 10 ^ -8- -7
v = 10 ^ 15 - 16
This is the third highest frequency EMR
Visible light wavelength and frequency
λ = 4-7 * 10^-7
v = 10 ^ 15
This is the fourth highest frequency EMR
IR wavelength and frequency
λ = 10 ^ -3-0
v = 10 ^ 9-15
This is the second lowest frequency EMR
Radio wavelength and frequency
λ = 10 ^ 0 +
v = 10 ^ 9-
This is the lowest frequency EMR
Light type by wavelength (least to greatest)
gamma rays, x-rays, UV, visible, IR, radio
Light type by energy (L-H)
Radio, IR, visible, UV, X-Rays, gamma rays
Photon Energy
E(photon) = h * v where h = Planck’s constant = 6.626 * 10-34
Rules for constructive/destructive interference
For constructive interference the change in position is d = n*λ
For destructive interference it is d = nλ/2 this is pi shifting because the light is pi radians out of sync
If light were particles what would Young’s double split look like
The particles of light would travel through the slits and not diffract or interfere
Distance between travel paths of bright spots for interference
This distance is equal to one wavelength. It is NOT the distance between the bright spots but the distance of travel paths
Distance between bright spots formula
x = dsinθ = m λ
x = distance between bright spots
θ = angle from the center to the bright spot.
d = distance between slits
m= mode/peak #
Why do diffraction gratings create dots
This is because at every point where there is not perfectly constructive interference there are equal but opposite wave points summating which create destructive interference.
Huygen’s Principle
This says that every point on a wavefront can be treated like a series of tiny propagation points. Thus if you have a single slit you will have a diffraction pattern because the part of the wavefront that makes it through the hole propagates with other wavefronts to constructively interfere
wavelength relationship for two mediums
λB = λa VB/VA = λA nA/nB
This says that the wavelength within medium B is given by the incident wavelength times the ratio of the refractive index of the first medium to the second medium.
Thin film interference criterion destructive and constructive
Constructive 2t = mλB = m λa VB/VA = m λA nA/nB
This says that twice the thickness of the thin film is equal to integers (m) of the wavelength fo light within the thin film medium
Destructive 2t = (1/2)mλB = m λa VB/2VA = m λA nA/2nB
Reflection types
Specular reflection refers to reflection that occurs on a flat surface so the incident and reflected rays are very predictable and related.
Diffuse reflection occurs on bumpy or uneven surface where the various directions of reflected rays interfere to produce colors
Specular and diffuse reflection happens on shiny things where parts are white (specular reflection) and others diffuse only the color of the object
Index of refraction
n = C/V
Special relativity E (electron)
E2=p2 + KE2 = p2c2 + m2c4 You can use this to find the momentum of a photon by using plancks equation for energy and the relationship between wavelength, frequency, and the speed of light.
momentum of a photon
p = h/λ
Photoelectric effect
This is the emission of electrons from the surface of a metal or other material with electrons in the conductance band when interacting with EMR. The process is photoemission and the e are photoelectrons
What is the relationship between a wave and KE
KE is proportional to amplitude. For light KE is proportional to frequency and not the amplitude (luminosity) but amplitude of light is proportional to more photoemissions so more charge transfer
Photoemission threshold frequency
This is the idea that for photoemissions to occur that there is some critical frequency of incident light that must be met.
ϕ/h = ν0 where ϕ is proportional to the bond energy of the electron that is emitted.
Louis de Broglie Idea
Broglie said that if light is wave or particle depending on how we treat it, why would an electron differ?
de Broglie wavelength
λe = h/p where p = momentum of electron
what is the meaning of ψ(x)?
In theory it is the position of a particle but it ends up being imaginary. we do know that the absolute value of ψ(x)2 is proportional to P(e-) @ (x,y,z,t)
and we know that ψ(x) collapses at measurements
three ways that electrons and light interact for photoemission
electrons will only change energy level if the incoming energy = hn where n are the varying modes and the energy is above the resonant frequency for release.
Electrons have a more negative potential energy closer to the nucleas. If the PE is positive the electron will be ejected.
If neither of the above criterion are met then the EMR goes through the electron.
