Midterm #2 Flashcards
A
Maxwell’s equations led to the prediction that ____
changing electric fields causes magnetism
How do electromagnetic waves travel?
Perpendicular to the direction they are traveling in. Transverse waves.
Every accelerated charge _____
radiates light
any electromagnetic wave produced by currents in wires is classified as a ____ wave
radio
infared light
produced by thermal motion and vibration/rotation of atoms. Heat lamps, night vision, heat tracking
Visible light
electronic transitions in atoms from one energy level to another
ultraviolet
also electronic energy transitions
X rays
high voltage discharges, occur when an electron drops to fill a vacancy in a lower orbital level. Medical diagnosis, airport security, cancer treatment
Gamma
nuclear origin. Cancer treatment, treat foods to prevent spoilage
Radio
produced by AC currents in wires, used for telecommunication, MRI. Can bend around obstacles easily because of their long wavelength
Microwaves
produced by LC circuits, grid on microwave door is smaller than the typical microwave
visible light range
390 to 700 (Red to Violet)
UV Rays uses
sterilize equipment, analytical tool, stimulate vitamin D production
Energy carried by a wave is proportional to
amplitude (or acceleration?) squared
Light travels in 3 ways
directly from source through empty space
through various media
reflected from a mirror
WHy does a windshield freeze before the windows?
objects on the side of the streets reflect heat back towards the windows, nothing is reflecting back on the windshield to warm it up
angles of reflection and incidence are measured from
the perpendicular line to the surface
diffuse reflection
light is diffused when it reflects from a rough surface
specular reflection
reflection off a smooth surface
Why can we see two fish at once in the corner of an aquarium?
light bends two different ways from the fish through the water and glass to your eyes
critical angle
incident angle that produces angle of refraction of 90 degrees
Total internal reflection
if the incident angle in the first medium is greater than the critical angle, all light is reflected back into the first medium. Fiber optics uses this because light doesn’t lose its amplitude.
Dispersion
spreading of white light into its full spectrum of wavelengths
rainbows
combo of refraction and reflection disperse sunlight into a continuous distribution of colors. Each water droplet produces cones of light. Inside is white light, rim disperses white light into colors
Virtual image
image on the same side of the lens as the object that can’t be projected onto a screen
ray tracing
from top of object draw a line parallel to the normal line
draw one through the center of the lens
and one that comes out parallel after being refracted. Where they meet is the image!
after tracing, if the image will either be upright, reduced, and virtual or inverted, magnified, real, or upright, magnified, virtual.
convex mirror only forms ___
virtual images
converging mirrors and lenses have a ____ focal length
positive
di is ____ for real images and ____ for virtual ones
positive, negative
Eye produces a ____ image on the retina
real
accomodation
adjustment of the focal length and power of the eye to create a real, clear image
eye has greatest power at ____ vision and least at ____ vision
close, far
Presbyopia
loss of the ability to accomodate eye
blind spot at
optic nerve
why do objects that are farther away look smaller?
they come into the eye at a smaller angle, so the eye perceives them as being smaller objects.
myopia
nearsighted, lens is too powerful or eye is too long
hyperopia
farsighted, lens is too weak or eye is too short
far point
distance to the farthest object that can be seen clearly
4 types of light receptors
1 rods, 3 cones
rods use
night vision, peripheral vision, motion changes
cones
central vision and color
hues of color
mixtures of wavelengths
color vision theory
one cone for red, yellow, blue, all hues a mix of those three
color of a lightsource is due to the ____ it produces
wavelength
microscopes
image formed by first lens in object for the second
magnification is the magnification of the individual lenses multiplied
when do interference and diffraction occur?
when the wavelength is comparable in size or larger than the structure its interacting with
Huygens principle
every point on a wavefront is composed of a wavelet, new wavefront= tangent to all the wavelets
explains what happens when waves go through a slit
correlation between wavelength and diffraction ability
larger wavelength= larger diffraction ability
Why does interference happen?
paths from each slit to a common point on the screen differ, so they interfere
What determines how far apart spots are on the double slit interference pattern?
Larger wavelength=farther apart
there are a limited # of possible interferences
diffraction grating
collection of evenly spaces parallel slits that produces an interference pattern similar to, but sharper than a double slit
constructive interference double slit formua
dsin0=my
single slit diffraction
broad central maximum with narrower and dimmer maxima to the sides. NO M=0
destructive interference single slit diffraction
Dsin0=my
D= width of slit
why does light diffract through a single slit?
it goes through in all possible directions so it interferes with itself
Rayleigh criterion
minimum sepparation between two light sources tha tmay be resolved into distinct light sources
Why can’t we perceive two headlights when a car is far away?
diffraction pattern of one is directly over the first minimum of the other, makes one light.
Resolvig power of our eyes ____ in the dark because _____
grows, our pupils get wider. According to Rayleighs criterion, larger D.
direction of polarization
parallel to the electric field of the EM wave
electric and magnetic fields of EM radiation are _____ to the direction of propogation
perpendicular
Special relativity
unaccelerated motion at the speed of light
inertial frame of referenceq
reference frame in which a body remains at rest and a body in motion moves at a constant speed in straight line
One in which newtons laws hold- object in rest remains at rest. One in motion remains in motion unless otherwise acted upon
two postulates of relativity
all laws of physics are the same and can be stated in their simplest forms in any inertial frame of reference
c is constant, independent of the relative motion of the source
Proper time
time measured by an observer at rest relative to the event being observed
proper length
length measured by observer who is at rest relative to both of the points
observer on earth sees a ____ spaceship
shortened
astronaut sees ____ earth and ____
shortened earth and shortened stars
observed wavelength gets _____ if object is moving toward observer. Gets ____ if moving away
shorter, longer
Turns red, turns blue
relativistic conservation of energy
conserved if you define it to include the possibility of mass changing into energy
mass= energy, so…
as energy is stored in an object, its mass increases. Can be destroyed to release energy
Why isn’t it possible for an object with mass to travel at the speed of light?
would require an infinite amount of work
correspondence principle
Quantum Mechanics makes same predictions as classical mechanics
Classical physics only applies when objects are
large, slow, and warm
evidence for quantization
blackbody radiation, atomic spectra
blackbody radiation
all objects above absolute zero emit EM radiation. As the intensity increases it does so with temperature. The hotter the object the more towards violet light it will shift.
Photoelectric effect
If you shine light of certain colors on metals you can eject electrons from the surface of the metal and create current. Magnitude of the current dependent on the frequency of the light. Electrons are only emitted when light has more energy than a specific threshold.
De Broglie Wavelength
all particles of matter also have a wavelength. Matter has the same interference characteristics as any other wave. Wavelength behavior becomes pronounced when it is similar in size to objects. Matter gives such a small wavelength you don’t notice.
heisenburg uncertainty principle
can’t know the position and momentum of an electron at the same time. Energy and time either.
Constructive interference
high probability of finding particle there
Constructive interference
high probability of finding particle there
brownian motion
evidence for atoms. Random motion of small particles in a fluid.
cathode ray experiment
discovery of electron
oil drop experiment
electron charge and mass
gold foil experiment
positively charged nucleus
rutherfords planetary model
Problems: accelerating charges emit EM radiation, which carries energy away and would cause e to spin into nucleus. Doesn’t explain atomic spectra
Bohr model
changed the orbits to be discrete quantified energy levels. Electrons can absorb or give off energy to move levels. Atomic spectra represent the orbital jump
smaller wavelength leads to ______ revolution
smaller
flourescence
atom is excited, gives off energy as it comes back town.
metastable state
stable state above the ground state where electrons settle and give off light. How lasers continuously emit light.
Zeeman effect
what appears as a single line on atomic spectra can be split by a magnetic field. SHows direction of electrons angular momentum. ALl spectral lines are doublets, showing that an orbital can only house two electrons with opposite spins
n
energy level
l
angular momentum
ml
angular momentum projection
ms
spin
