1. Study Points Define blackbody radiation.
Draw two graphs of intensity vs wavelength for the low temperature object (reddish) and the high temperature object (bluish). What happens to the graph if the temperature of the body increases?
Define and differentiate between the following: atom, element, molecule
Identify the three basic particles in an atom. Know whether their charge is positive or negative or neutral. Know their approximate relative masses (not the mass itself, just how they compare). Know where each is located in the atom.
Describe or sketch a simple model of the atom (the Bohr model) including permitted orbits.
Given a model of the atom, show which jumps correspond to emission spectra and which to absorption spectra.
Given a model of the atom showing several energy levels, identify which photon comes from which electron transition.
What information can astronomers obtain from the spectrum of a star, galaxy or gas cloud?
What did Annie Cannon contribute to the study of spectra? Cecilia Payne?
State the two chief components of stars. What percent is each?
Discuss how astronomers can tell what elements are in a gas cloud or in a star.
Left off on slide 24 (skip video)
Demos: Tennis balls, Box/chair to stand on (step stool), scratch papers for attendance; Cosmos Episode 8, variac and dimmable light bulb (Edison and LED)

2. Blackbody Radiation Atoms and Light1 3 2

3. Blackbody Radiation Definition: Radiation emitted by a heated object*
When not heated, the object is black
When heated, the object varies in color depending on the temperature
Continuous spectrum
A blackbody absorbs and emits radiation
Cooler object – less radiation
Hotter object – more radiation
Spectra
Wavelength & Color depends on Temperature
A black body is an object that is a perfect absorber and emitter of radiation

4. Blackbody Radiation Examples: Incandescent light bulb
Filament changes color as it is heated
Hot lava
Sun and other stars
Heated metal
Quickly heated ice cube glows
Spectra
No blackbody is perfect but these are pretty good examples
Visible blackbody radiation; things that glow when heated
Humans are not blackbody radiators; convert UV to infrared; humans convert most light to infrared
Shiny surface and glass do not absorb visible radiation well; UV and infrared do not go through glass
Any body above absolute zero will radiate some

5. Blackbody Radiation Examples Spectra Cooler Objects
Emit less radiation
Appear reddish
Hotter Objects
Emit more radiation
Appear yellowish
Spectra
Pass out Papers
Wavelength & Color depends on Temperature
A black body is an object that is a perfect absorber and emitter of radiation

6. Light Bulb Filament & Demonstration Solve: Are there vibrations of the atoms in the filament?
Are there many atoms or a few atoms in the metal filament?
True or False: Each atom vibrates at some frequency.
True or False: All atoms vibrate at the same frequency.
Why does an object change color when heated? Explain.
Are there vibrations of the atoms in the filament?
Demo: light bulbs and variable voltage
Show demo of variac and adjustable voltage going into the light bulb (Edison or LED) LED-no filament, electroluminescence from electrons giving off photons
Handout papers and form groups:
Atom is a basic unit of an element (chemical element in periodic table)

7. Light Bulb Filament & Demonstration Solve: Are there vibrations of the atoms in the filament?
1. Are there many atoms or a few atoms in the metal filament?
MANY ATOMS
Show demo of variac and adjustable voltage going into the light bulb (Edison or LED) LED-no filament, electroluminescence from electrons giving off photons
Handout papers and form groups:
Atom is a basic unit of an element (chemical element in periodic table)

8. Light Bulb Filament Solve: Are there vibrations of the atoms in the filament?
1. MANY ATOMS in the metal filament.
2. True or False: Each atom vibrates at some frequency.
TRUE

9. Light Bulb Filament Solve: Are there vibrations of the atoms in the filament?
1. MANY ATOMS in the metal filament.
2. Each atom VIBRATES at some frequency.
3. True or False: All atoms vibrate at the same frequency.
FALSE
Not all vibrate at the same frequency
Many different frequencies
4. What is the wavelength of red and blue light? 700nm and 400nm

10. Light Bulb Filament Solve: Are there vibrations of the atoms in the filament?
1. MANY ATOMS in the metal filament.
2. Each atom VIBRATES at some frequency.
3. Atoms vibrate at the DIFFERENT frequencies.
4. Why does an object change color when heated? Explain.
Different frequencies correspond to different wavelengths and display different colors.
Blue light = 400 nm
Red light = 700 nm
430–790 THz (tera hertz, 10^12) for red to blue light frequencies (wavelengths: 700 to 400nm)

11. Light Bulb Filament Solve: Are there vibrations of the atoms in the filament?
1. MANY ATOMS in the metal filament.
2. Each atom VIBRATES at some frequency.
3. Atoms vibrate at the DIFFERENT frequencies.
4. Why does an object change color when heated? Explain.
Different frequencies correspond to different wavelengths and display different colors.
Blue light = 400 nm
Red light = 700 nm
5. Are there vibrations of the atoms in the filament?
YES!
430–790 THz (tera hertz, 10^12) for red to blue light frequencies (wavelengths: 700 to 400nm)

12. Blackbody Radiation Examples: Spectra Side Note:
Side Note:
Intensity = Energy/surface area
Temperature α Energy
Spectra
Atoms vibrating at different frequencies display different colors.
Intensity, Energy and Temperature all correlate together.
No green stars because there is blue and red present so it looks white

13. Which star is hottest? How do you know?

14. Which star is hottest? How do you know?
Hotter object (higher temperature) has:
More overall radiation (intensity)*
Higher peak*
More blue color
Be able to draw Intensity vs. Wavelength graphs*
And it is also blue-ish!

15. Blackbody Radiation in Stars
Watch simulation

16. Spectrum of the Sun What do you know from this spectrum?
Absorption – hot dense object with a gas cloud
Mix of gases (but which ones?)
How did we figure this out…

18. Spectra Other stars show similar but not identical line patterns.
So why are there lines in the spectra at all?
What do those lines mean?
Spectra

19. Spectra of stars (differences)
Astronomy in late 1800’s and early 1900’s.
Each stripe of light is the spectrum of one star.
Note that each spectrum tapers off at the ends like the blackbody graphs.
Note the different lines in each spectrum for different stars.

20. Intensity difference

21. Line differences are element differences

22. Annie Cannon* Spectra Harvard around 1900
Sorted thousands of stars by their patterns of spectra lines.
Discovered patterns among star spectra
Spectra lines are different for different elements*
Spectra
Hotter
Around 1900 ( )
Scarlet fever, lost most hearing
Never married, no kids
Born in Delaware
Cannon's mother was the first person to teach her the constellations and encouraged her to become whatever she wanted, suggesting for her to pursue studies in mathematics, chemistry, and biology at Wellesley College
Astronomy and photography
Taught physics at Wellesley
Radcliffe women’s college to get access to Harvard observatory: Pickering’s women
Sorted and categorized 225,000 stars
Cooler UV
Longer λ
λs?, visible?, Temperatures?

23. Annie Cannon { { { { { { Spectra Hotter O B Blue A F G K Cooler M Red
Color today; black and white then.
Oh Be A Fine Girl, Kiss Me
Cooler { M
Red
Lines used to categorize wavelength & temperature
Still used today and extended past M for darker red and brown stars.

24. Spectra So why are there lines in the spectra at all? And
What do those lines mean?
Start “Ring of Truth – Doubt” at about 4:30min

25. Definitions Atom* Element* Molecule* Spectra
Basic unit of a chemical element
Has protons, neutrons, & electrons
Element*
More than 100 substances that cannot be broken down any simpler
Molecule*
Group of atoms
Spectra
Atom is singular and the plural is molecule
Can have an atom of hydrogen and a molecule of hydrogen (the element)

26. Atoms Protons – positive charge ( + ); larger mass*
Neutrons – neutral, no charge; larger mass*
Electrons – negative charge ( - ); smaller mass*
Nucleus
protons and neutrons*
Surrounded by
“orbiting” electrons*
Spectra
Mass of proton : x 10^(-27) kg  Mass of neutron: x 10^(-27) kg  Mass of electron: x10^(-27) kg

27. Study of atoms and subatomic particles
Quantum Mechanics
Study of atoms and subatomic particles
Bohr Model
(be able to draw this*)
Ground state -
Lowest energy level
Each shell can contain only a fixed number of electrons: The first shell can hold up to two electrons, the second shell can hold up to eight (2 + 6) electrons, the third shell can hold up to 18 (2 + 6 + 10) and so on. The general formula is that the nth shell can in principle hold up to 2(n2) electrons.
1. Electrons have certain “orbits” and not others
2. Orbits are closer together as you get further from the nucleus

28. Quantum Mechanics
Absorb = take in (ex. Increase energy)
Emit = give off (ex. Decrease energy)
Emission Spectrum: When an electron jumps “down”, it emits all the energy at once in a bundle called a photon (the energy is quantized as a packet). Electron emits energy.*
Absorption Spectrum: If an electron absorbs a photon of just the right energy, it jumps “up”. Electron absorbs energy.*
Whatever is emitted is the color given off and the color we see
energy of jumps are measured from nucleus (highest energy has most distance from nucleus)
Demo of colored tennis balls here: purple, blue, green together; then red, orange, yellow (purple highest energy – 2 levels, red – lowest energy)

29. Of the electron jumps shown, which number of jump(s)
EMITS (gives off) a photon?

30. Of the electron jumps shown, which number of jump(s)
EMITS (gives off) a photon?*
2 and 3
Decrease in energy

31. Of the electron jumps shown, which number of jump
ABSORBS (takes in) a photon?

32. Of the electron jumps shown, which number of jump
ABSORBS (takes in) a photon?* 1
Increase in energy

33. Which jump corresponds to emitting a blue photon?
For the atom shown, a blue and a green photon are emitted and a red photon is absorbed.
Which jump corresponds to emitting a blue photon?
Which jump corresponds to emitting a green photon?
Which jump corresponds to absorbing a red photon?
For the atom shown, a blue and a green photon are emitted and a red photon is absorbed.*
Which jump corresponds to emitting a blue photon?
Which jump corresponds to emitting a green photon?
Which jump corresponds to absorbing a red photon?
Objects appear whatever color is emitted. If object absorbs all color, it is black in appearance. If object emits all color, it is white.
Demo in class with colored tennis balls
(purple greatest) Blue is highest energy
Next green
Then yellow
Then orange
Lowest energy is red

34. Which jump corresponds to emitting a blue photon?
For the atom shown, a blue and a green photon are emitted and a red photon is absorbed.
Which jump corresponds to emitting a blue photon?
Which jump corresponds to emitting a green photon?
Which jump corresponds to absorbing a red photon?
For the atom shown, a blue and a green photon are emitted and a red photon is absorbed.*
Which jump corresponds to emitting a blue photon? 2
Which jump corresponds to emitting a green photon? 3
Which jump corresponds to absorbing a red photon? 1
Demo in class with colored tennis balls; energy of jumps are measured from nucleus (highest energy has most distance from nucleus)
(purple greatest) Blue is highest energy
Next green
Then yellow
Then orange
Lowest energy is red

35. Cecilia Payne-Gaposchkin*
Surveyed star spectra
Discovered stars are about 90% hydrogen and 10% helium*
( ) Completed college at Cambridge in England but was not awarded a degree (1919 and didn’t get women’s degrees until 1948 there)
Went to US where better opportunities for women awarded the first phd from Radcliffe/Harvard in astronomy. possibly the greatest PhD dissertations ever written
Married and had three kids.
Harvard had female students in 1963, 1975 merged 2 schools (1st black student graduated in 1870)
First female full professor at Harvard and first female department head at Harvard (in astronomy). ( )
about 0.1% other elements
(maybe add Henrietta Swan Leavitts, Radcliffe, A- in astronomy 4th year of college, lost hearing, discovered Cepheid variable stars’ relationship between luminosity and period which led to the calculations of more distant galaxies)

36. Spectra Lines Tell us what elements are in the spectra (Annie Cannon)*
Tells us how much of each element is in the spectra (Cecelia Payne-Gaposchkin)*

37. (WATCH) Cosmos: A Spacetime Odyssey Episode 8: Sisters of the Sun (2014)
Edward Charles Pickering hired 80+ women to work for him at the Harvard Observatory
Cosmos episode 8 (10 min): time 8:10 to 18:20
Edward Charles Pickering hired women at Harvard to work for him. They got paid about half of what men made doing similar work
Cosmos: A Spactime Odyssey (2014) with Neil deGrasse Tyson, Episode 8: Sisters of the Sun

38. Homework & Observations
Continue flashcards of STUDY POINTS
D2L Quiz 6 open. Quizzes 5-8 for Test 2
Observations:
Moon Phases Due Mar. 7 (10 points) Observe 4 phases & record in table
- visible Moon times
Student Success Day Due Feb. 28 TODAY! (5 points) Attend at least 1 session
Sunset – Part 2 Start Apr. 9; Due Apr. 30 (10 points) Take 2nd picture of sunset
Astrophysics Lecture or Report Due Apr. 16 (10 points) Attend U of M lecture on Apr. 11 OR write report
Astronomy News Report Due May 14 (20 points) Report evaluating astronomy in the news
Planetarium Due May 14 (10 points) Go to a planetarium show
Stargazing Due May 14 (20 points) Go stargazing & write report
Telescope Due May 14 (20 points) Look through a telescope in Twin Cities
Moon Craters Due May 14 (10 points) See moon craters through a telescope OR binoculars & write report
No Lab today – get ready for lab next week
Mar. 5 & 7 – Dim. Anal. & Sig. Fig. QUIZ & Doppler Lab
Tutor Oskar in T3200 Tue, Wed, Fri – class website has hours
Clarify observation locations and expectations
Grades: let me know if there are any mistakes
Update on student success day