Electromagnetic Radiation (EMR) Flashcards
what produced electromagnetic radiation
accelerating charges
does EMR act like a particle or a wave?
both, either
when does EMR act like a wave
in diffraction and interference. if the frequency is less than visible light
when does EMR act like a particle
when the frequency is greater than visible light
characteristics of red light (left side of visible spectrum)
about 700 nm, low energy, low frequency, long wavelength
characteristics of violet light (right side of visible spectrum)
about 400 nm, high energy, high frequency, short wavelength
what is ionizing radiation
EMR past visible light (ultraviolet, x-rays, and gamma radiation)
what is the universal wave equation
c = λf it works for all EMR
what speed does EMR travel at
the speed of light, 3.00 x 10^8 m/s
What was the Michelson experiment
he used a rotating, 8 sided disk and a mirror 35km (?) away to measure the speed of light. the light bounced off one flat side of the disk, hit the mirror and traveled back to hit a flat side of the disk.
refraction
the changing of direction or bending of a ray as it passes from one medium to another. it is caused by a sudden change in speed
when does speed decrease in refraction
when θ1 > θ2 . the wave is faster in medium 1
when does speed increase in refraction
when θ1 < θ2. the wave is slower in medium 1
what does not change in Snell’s law
frequency
dispersion
the separation of EMR into individual wavelengths. it occurs when a wave passes from one medium to another. (forms a spectrum)
What happens when EMR travels from a high to low refractive index
it bends away from the normal line
critical angle
the greatest angle at which a ray of light can strike the boundary between the 2 mediums without causing total internal reflection.
when does total internal reflection occur
when the incident angle is greater than the critical angle
what do lenses and mirrors do
they redirect the path of EMR and form images
what are the possible characteristics of an image
Attitude - inverted or upright
Type - real or virtual
Size - larger or smaller
Diffraction
the spreading out of a wave as it passes a corner or through an opening
who thought light was particles
Newton
who thought light was waves
Huygens
What experiment proved that EMR could behave as a wave
Thomas Young’s double slit diffraction experiment
the higher the energy and frequency the
shorter the wavelength
radio waves
used in communication, wavelength = 10^4 - 10^-2 m
Microwaves
made by oscillation of electrons in vacuum tubes, used in radar, heating, communicating, wavelength = 10^-1 - 10^-4 m.
wavelength of red light
700 - 750 nm
wavelength of blue/violet light
400 - 450 nm
wavelength of green light
550 nm
infared radiation
made by molecular motion, transitions of valence electrons, used for night vision, identifying heat sources, wavelength = 10^-3 - 10^-7
Visible light
made by valence electrons dropping from high energy to low energy. wavelength = 400-700nm
ultraviolet
made by higher energy transitions involving valence electrons, ionizing radiation, wavelength = 4.0x10^-7 - 4.0x10^-9 m
x-rays
made by sudden deceleration of very high speed electrons, ionizing radiation, wavelength = 10^-9 - 10^-12 m
gamma rays
made by nuclear reactions, ionizing radiation, penetrates matter very deeply, wavelength = 10^-11 - 10^-16
Galileo’s experiment
did not work. he tried to measure the speed of light with two lanterns a mile apart but only determined that light was too fast to measure this way.
who measured the speed of light by observing eclipses of Jupiter’s moon Io
Olaus Romer and Chrisitan Huygens
types of mirrors
concave converging and convex diverging
center of curvature
point that represents the center of the sphere from which the mirror was cut
Vertex
geometric center of curved mirror surface
Focal point
point where light rays converge or appear to diverge from after being reflected
what is something all real images have in common
they are all inverted
what is something all virtual images have in common
they are upright
the focal length of converging mirrors is
positive
the focal length of diverging mirrors is
negative
the more a medium slows down light,
the greater the index of refraction
When light passes into a medium with a larger index of refraction
it bends towards the normal (FST)
When light passes into a medium with a lower index of refraction
it bends away from the normal (SFA)
what is polarization evidence of
that light is a transverse wave
what does polarized light do
it vibrates in the same plane
what color light is more affected by refraction
blue/violet
what color light is more affected by defraction
red
in which phenomena does EMR act like a wave
diffraction and interference (the double slit experiment), and polarization
in which phenomena does EMR act like a particle
the Photoelectric Effect and the Compton Effect
threshold frequency
the minimum frequency needed to release electrons from the metal’s surface
work function
the minimum amount of energy needed for electrons to leave the surface of a metal
Photoelectric formula
Ephoton = Ek + W
photocurrent vs frequency graph
rectangular. there are no electrons before the threshold frequency, then the frequency has no effect
photocurrent vs intensity graph
linear, for each photon, one electron is released
photocurrent vs stopping voltage graph
curved down (inverse), electrons originating below surface have greater W and smaller Ek and require a smaller stopping voltage.
what is light thought of in the Compton effect
a mass-less particle that has momentum
