Ast 109 Lesson 15
Transitions of Electrons
-Electrons change orbits and energies, as photons come and go. -A photon must have the exact amount of energy to complete the difference in energy between the two transitioning orbits. Example with Hydrogen: for an electron in Hydrogen to go from n = 1 to n = 2, it takes 10 electron volts of energy.
Nucleus
2 x 10^-5 Angstroms or 2 x 10^-15 m
Blackbody Radiation
A perfectly absorbing body of energy. It is black at all wavelengths, meaning it doesn't reflect any photons. -Radiates red or orange when heated. -The continuum shape only depends on the temperature of the body Example: The sun
Continuum Spectrum
A smooth intensity curve with no dropouts or spikes. -intensity depends on wavelength and varies smoothly -It only occurs from a dense, hot object---black body star/object
Ions are charged atoms. How can this be?
An ion has fewer electrons than protons.
Ions
Atoms that are charged because the number of protons is not equal to the number of electrons. Extra electrons causes the ___ to be negative, and missing electrons causes the ___ to be positive. Example: Comet tails
What situation would you give an absorption spectrum?
Cool, thin gas between you and the light source.
Planck's Law
E = hc/wavelength E = hfrequency h = Planck's constant = 6.6 x 10^-34 joules per second c = speed of light = 3 x 10^8 meters per second wavelength is in meters
Spectrum
From using a spectrograph we can find the elements present and their amount, if there is any motion of a star through shifting of spectral lines, temperatures from lines that are present or absent, masses, and ages.
Electrons
Have a negative charge and their orbits are about 1.5 angstroms apart.
Protons
Have a positive electric charge
Neutrons
Have no electric charge
What situation would you give a continuum spectrum?
Hot, dense gas as your light source (a black body star)
What situation would you give an emission spectrum?
Hot, thin gas to the side of your light source.
Example of Planck's Law
Hydrogen Lyman series of lines: Ly(alpha) = 1215 Angstroms Ly(beta) = 1026 Angstroms: this one has more energy because the wavelengths are shorter.
Emission Spectrum From Clouds
If a low density cloud is heated up by nearby stars, it will radiate for us to see. The radiation is at well-defined wavelengths, depending on the elements present. In a black spectrum, emission lines are bright lines showing up between large dark gaps.
Light Scattering By Gas
Light from a star is scattered or absorbed when passing through a gas or dust cloud. When analyzing the spectrograph, the dark lines breaking up the continuum in certain spots are absorption lines.
An atom is neutral if the number of _______ is equal to the number _________.
Protons, electrons
Absorption Spectrum From Stars
The atmosphere of a star is cooler than the surface, so it acts like a cloud. The absorption lines of the atmosphere are in continuum from the surface. From these lines we can tell the temperature and the makeup of the atmosphere.
Wien's Displacement Law
The max wavelength is the wavelength peak of the black body continuum. -As temperature increases, the peak moves to shorter wavelengths. -wavelength max = 3 x 10^7 Angstroms/Temperature
Isotopes
The number of neutrons determines the _______ and weight of an atom. The number of protons determines the element. Example. Hydrogen has 1p and 0n. Deuterium: 1p 1n. Tritium: 1p 2n.
Allowed Orbits
The principle that only certain energy levels are "allowed" in an atom of a specific element. The electron orbit is very fuzzy and resembles a cloud around the nucleus.
Temperature-Color Relationship
The principle that the bluer an object in the universe, the hotter its temperature. -red hot: 2,000 - 4,000 degrees K -blue hot: 10,000 degrees K or more
Atoms
The smallest components of an element with the characteristics of that element shown through a difference in the number of protons.
Molecules
Two or more atoms linked by sharing electrons.
Absorption
When an electron gains a photon's energy and jumps to a higher orbit.
Emission
When an electron loses energy and drops to a lower orbit.
Blue Hot ~ _____ Hot
White: When looking at the sky, mostly all of the stars appear white, even if they are blue, or a different color (besides red which is easier to distinguish).
Electron Volt
eV: 1.6 x 10^-18 joules
The ______ the wavelength, the _____ the energy
longer, lower
