Date post: | 16-Dec-2015 |
Category: |
Documents |
Upload: | myah-peffer |
View: | 214 times |
Download: | 0 times |
Uses of Light Astronomers use light as a tool to “dissect” celestial objects
Only direct information we can get!
Collect light with various instruments
Study light to determine sources
Light Sources
Atoms or parts of the atom are the source of all light
Behavior of particles in Atom generates light
What are these particles?
Parts of the Atom
Atoms are building blocks of matter
Nucleus Protons – Positive Charge Neutrons – Neutral
Orbits Electrons – Negative Charge
Building Blocks
Elements-pure substances Atoms- smallest part of an element
Compound- chemically joined elements
Molecule- smallest part of a compound
Elements
Periodic Table ID’s are Atomic Number (Z) Z=number of protons Atomic Mass (A) Number of Protons + Number of Neutrons
Elements
Neutral Atoms have same # of electrons and protons
Ions have lost or gained some electrons
Isotopes have lost or gained some neutrons
Get Excited
Electrons naturally orbit in lowest energy state
Ground State If atom absorbs some energy the electron can move to a larger orbit
Excited Electron
Excited Atoms
Atoms gain energy Excited (but not ionized) atoms
Electrons move away from nucleus but are still orbiting
Excited Atoms
Electron absorbs energy to “jump up”
Electron releases energy to “fall down”
This Energy is Light!
Spectra
Light is released This is the Spectra of the atom
Unique Distinct Fingerprint for Elements and Compounds
Absorption Spectra Similar to Continuous Spectra
Dark gaps where colors are missing
Also Spectral Lines
Unique for Each Element
Kirchhoff’s Rules
Describes conditions needed to form the 3 types of spectra
Can be related to Astrophysical conditions
We can infer information from type of spectra
Rule #3
Hot, opaque solid with a cool gas cloud between the source and viewer
Absorption Spectra
The Sun
Spectra Clues
Looking at the spectrum of a star can help us identify what elements are in it
Can also tell us about temperature and brightness
Gives clues to hidden processes within the star
Lots of Light
“Light” is any EM wave EM= electromagnetic Has both an electric part and a magnetic part
Not always “visible” to us Entire spectrum is huge
Wavelength Length from one part of a wave to the next identical part
Can be measured in any length unit
Astronomers use Angstroms 1Å=.0000000001 meters (10-10m)
Frequency f
The # of waves that pass by a point in a given amount of time
# of waves per second Measured in Hertz Hz
Wavelength and Frequency Related! Long Wavelength = Low frequency
Short Wavelength = High frequency
Wavelength increases, frequency decreases
Light Waves
Wavelength x Frequency= Wave Speed
x f = c (speed of light) c is same for every light wave
So what separates them is frequency and wavelength
Electromagnetic Spectrum There is a continuous spectrum of light
Visible light (colors) are included in this
They are only a very very small part
EM Spectrum
Gamma Rays
X-rays
Ultraviolet
Visible
Infrared
Radio
← ← ← Wavelength increasing, Frequency decreasing
Energy of Light
Photons of light carry energy This energy is related to wavelength and frequency
As frequency goes up, energy goes up, since more photons are arriving
As wavelength goes up, energy goes down
Energy of Light
If you double frequency, you double energy
Or, if you halve the wavelength, you double the energy