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52 Cards in this Set

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What is the wave nature of light?
a way to transfer energy from place without the physical movement of material from one location to another
Wave characteristics:

Distance between successive wave peaks
Wavelength
Wave charactistics:

Time between passing wave peaks
Period
Wave characteristics:

Number of wave peaks passing per unit time (1/Period)
frequency
wave characteristics:

wavelength x frequency
Wave speed
what is the speed of light?
3e8 m/s
Sound waves travel by vibrating the molecules between the source and listener. Is this how light travels?
Light does not require a medium in which to travel… Light can travel thru a vacuum.
The changing position of a charged particle creates
“waves” in the field lines.
Moving charges also produce
Magnetic fields (accelerating charges).
magnetic fields force charged particles
to move (to accelerate)
** WHAT CAUSES LIGHT? **
E&M Waves produce LIGHT!
If Electromagnetic waves creat light, what creates electricmagnetic waves?
Accelerating charges (electrons, protons)
The waves of electric field and that of the magnetic field propogate...
at right angles to one another.
While the electric field and magnetic field are at right angles to one another. What direction is the wave's motion?
90 degrees from both the electric field and 90 degrees from the magnetic field.
What is the range of the EM spectrum, from least to most energy?
Radio, Infared, Visible (Red to Violet), Ultraviolet, X-ray, Gamma
As energy increases, what happens to the wavelength? frequency?
wavelength decreases as energy increases. Frequency increases as energy increases.
Where would microwaves fall on the EM spectrum?
Between Radio waves and infared.
Why are optical telescopes built on hill tops or at high elevation?
Because the ATMOSPHERE ABSORBS some of the light coming from space. Minimizing the atmospheric content between the telescope and space increases the amount of light it will recieve.
What makes objects emit EM radiation?
when charged particles change their rate of motion, they emit EM radiation.
measures the amount of motion of the particles
temperature
In other words, the hotter the object...
the higher its temperature and the MORE movement it's particles have.
All solid/dense objects emit radiation having a characteristic spectrum called
blackbody
Hotter blackbodies are (color)
Bluer and brighter
If all bodies emit EM waves, why cant we see one another in a dark room?
Because the EM radiation given off by the body is in the IR not in the visible spectrum.
Why is the sun yellow?
because AT ITS MAXIMUM INTENSITY, it's wavelength is in the yellow visible region.
Wien's law states that Hotter bodies radiate more strongly at..
SHORTER WAVELENGTHS (BLUER)
Mathematically, what is Wien's law?
Wavelength= .29 cm/ Temp(K)
Why is wien's law so important?
Knowing a star's wavelength by simply observing the light it emits, we can determine the star's TEMPERATURE!
Stefan's law states that hotter blackbodies are...
brighter (at any wavelength).
Mathematically, what is stefan's law?
F = sigma x T4

F= flux
sigma= constant
Experimentally, how is a continuous spectrum produced?
By passing white light through a slit and through a prism.
Experimentally, how is a emission line spectra created?
Passing the light from a heated gas through a slit.
What does each unique pattern of lines tell us?
the chemical composition of the gas. Each compound produces a unique spectra.
Experimentally, how is an absorption line spectrum created?
passing hot light through a cooler gas and passing it through a slit.
Kirchoff's Laws:

First law: hot, dense gasses or solids produce a
Continuous spectrum (light bulb)
Kirchoff's Laws:

Second law- hot rarefied gases produce an...
emission line spectrum.
Kirchoff's Laws:

Third law- Cool gas in front of a hot continuous source produces an
absorption line spectrum
What are the three subatomic particles that make up an atom?
electrons, protons, and neutrons.
Atoms are mostly....
empty space. the protons and neutrons are squeezed into a tiny space whereas the electrons circle widely around. EMPTY SPACE IN BETWEEN!
what makes each atom of a given element unique?
The number of protons and ELECTRONS!
*** The Bohr Hydrogen model states that...
every hydrogen atom has one electron circling a proton.
How did Bohr suggest the electron remained in orbit?
by the Columb effect (inverse squared law)
Bohr suggested that electrons can orbit in particular energy states. How would an electron change energy states?
Electrons would go from the energy state to more energetic states by absorbing energy (usually a photon). In order to return to the ground state the electron releases this energy (usually in the form of light).
That energy (which is added or released when the electron changes orbit levels) is
photons of light
Atoms can only absorb or emit photons having energy exactly equal to
the energy difference between electron orbits
High energy photons correspond to short wavelength light and may boost the electron so much that it is completely ejected from the atom! This process is called?
Ionization
TO CLARIFY: Every e- “transition” corresponds to
a unique wavelength.
In modern quantum mechanics:
Electrons are not just particles, but also
waves, without exact locations
Moving sources, like fire trucks and race cars, change pitch as they go by… This phenomenon is known as?
Doppler effect
As an object passes you, does the pitch go up or down
down
Doppler shift: Stars moving toward us appear what color? Those moving away appear what color?
Blue (Blue-shifted)

Red (Red-shifted)
What can we determine by spectroscopy of the light we observe from stars?
Chemical composition (spectral lines)
Temperature (blackbody)
Velocity (doppler)
Rotation rate (doppler)
Pressure (spectral lines)
Magnetic field (Zeeman effect)