3Opener – Quick WriteWe are going to write for exactly one minute on a certain topic (to be shown once the bell rings).You may do this in your notes.On our opener for today, put “quick write”Don’t pick up your pencils until I tell you to…This is excellent practice for standardized tests (like the ACT/MME) The purpose is for you to get ideas out of your head and down on paper. Of course, it must be related to the question. See how many words you can get in 60 seconds! We will count them at the end.
4Opener – Quick WriteExplain what the difference is between potential energy and kinetic energy, and how one can be converted to the other.
5Light Light is very much still a mystery Visible light is only a small part of all the different types of lightElectromagnetic Radiation: Includes gamma rays, X-rays, ultraviolet light, infrared rays, microwaves, radar waves, television/radio wavesAll types of light travel at the same speed (300,000 km/s)
9What is Light?Light behaves in some ways like a wave and in some ways like a particleWaves: think of waves in the waterWavelength: the distance from one crest of a wave to the nextDifferent wavelengths = different colorsSo violet and blue have very short wavelengths, red and orange have very long wavelengths
10Opener How much of light can we see? What other kinds of “light” are there? (name as many as you can remember)
11Light as a WaveThink of dropping a rock into a completely still pool of water…what happens?Now think about at the beach, the breakwater…what happens to the waves?The same thing happens with lightThat’s why if a light is on in the hallway, it still partially lights up our roomLight “bends”
12Photons Photons: streams of “light particles” Because light sometimes acts like its made of particles instead of wavesThink of very small bullets fired from a machine gun…they have a force, they can push on matterThe force from light is called radiation pressureWhere did we hear that before???Each photon has a specific amount of energyShorter wavelengths have more energy than longer wavelengths
13The Doppler EffectDoppler effect: the perceived change in wavelength from a source that is moving.Sound: When an ambulance is approaching you, the siren sounds higher in pitch (because the waves are closer together)Light: When an object is approaching, the light from it is appears redder than it actually isAstronomy: Can determine whether stars are moving toward us or away from us
14Brief Review Is light a wave or a particle? How does light act like a wave?How does light act like a particle?What is the Doppler effect?
15Tools for Studying Space Astronomy (2)ES 24.2Day
16TelescopesRefracting Telescopes: uses a lens to bend light
17TelescopesReflecting Telescopes: Uses a mirror to focus light in front of the mirror
18TelescopesRadio Telescopes: Focus incoming radio waves
20OpenerHow does light act like a wave? Give an example (draw a picture if you want)What are the particles of light that carry radiant energy called?
21Reflection, refraction Refraction: light bends through glassReflection: use of mirrorsWhen you shine a light at a mirror, what happens? What if its at an angle?Angle of incidence = angle of reflection
22Light and Telescopes What if you have a mirror that is curved? Concave Convex(light unites) (light diverges)
23Concave/convexConcave ConvexThe front of a spoon The back of a spoon
24LightWe can only see things because light is being reflected off of themSo when we see a blue object, its because the blue light is being reflected. All the other colors are being absorbed.When waves pass into a different medium (substance), they change speedsWhy don’t they change wavelengths?When light passes into a different medium (substance), it is refracted (bent).Think of light going through water…it gets bent, distorted
25Other electromagnetic waves Sonar is using reflected sound waves underwaterBats use echolocation (similar)Know the general order of the different types of electromagnetic waves! We’ll be getting a worksheet on it…
27WavesWave: Repeating movement that transfers energy through matter or spaceSo the wave travels only as long as it has energy to carryWaves on a lake don’t actually move water…what do they move?Think of a boat and a bunch of waves hit it, after they pass its in nearly the same place
28Mechanical WavesTransverse waves: matter moves at right angles to the energy (water, light, and electromagnetic waves)Compressional waves: matter moves in same direction as energy (springs, and sound)
29Parts of a wave Crest Trough Wavelength Frequency: The # of wavelengths that pass by each second1 Hz = 1 wavelength per second\Amplitude: the height
30Wavespeed v = fλ v = velocity (m/s) f = frequency (Hz) λ = wavelength (m)If we increase f, then λ must decreaseIf we increase λ, then f must decreaseIf the wave passes through a medium (substance) with different density, the speed may change
31WavelengthThe lowest pitched sounds humans can hear have frequency of 20 Hz. What Is the wavelength of those sound waves if their speed is 340 m/s?
32WavelengthThe speed of light is 300,000 m/s. Find the frequency of blue light (about 400 nm, or m) and of red light (about 800 nm, or m).
34OpenerSuppose light is reflected from a surface and you decrease the angle of incidence by 0.5 (cut it in half). What will happen to the angle of reflection?What color(s) wavelength is/are being reflected from a green book? What color(s) is/are being absorbed?
35Retrograde Motion of Mars Lots of graphingTo see how Mars moves in the night sky in relation to the starsYou may work in groups of 3 (your choice)Use different colors!Due: Monday (but you may turn it in today if you get done)
42Nuclear Fusion Nuclear Fusion: how the sun gives energy During nuclear fusion, 4 hydrogen (H) atoms combine to form one helium (He) atom4 H atoms have more mass than 1 He atom… so there’s leftover massE = mc2
43The Sun’s Future The sun can “live” about 10 billion years Its been around for 4.5 billion yearsSo it will be around for another 5.5 billion yearsSun changesSun formedNow4.5 billion years5.5 billion years10 billion years
44Our Sun Our sun is a main-sequence star We’ll learn more about this later…In about 5.5 billion years, it will become a red giantDon’t worry, we’ve got time!
45Review Where does the sun’s energy come from? What are sunspots? What is solar wind?How long will the sun stay in its present form?
46Waves Worksheet We’re going to do some of these in class Some individually, some togetherThen we’ll finish it as homework
48OpenerWhere does the sun’s energy come from (what is the process called?)How much longer will the sun stay in its present form?What is the difference between sunspots and solar wind?5th and 6th hours: Your Mars Lab is due today! Please turn it in!
49HW – Waves Worksheet Go over answers in your “natural groups of four” The person who will read their answers for the rest of the group will be the person who….We’ll go over any questions in a moment, but make sure you circle any that you don’t agree on!
50Stars Nearest star: Proxima Centari – 4.2 light years away! Stars are light years away!1 light year = 9.5 trillion kilometersColor relates to temperature…think of looking into a fire, what color is the middle of the fire? The outside?Blue stars = very hotRed stars = cooler
52Hertzsprung-Russell Diagram The Hertzsprung-Russell diagram shows the relationship between absolute magnitude and temperature (of stars)Shows dwarf stars, giants/supergiants, and main-sequence starsAbout 90% of stars on HR diagram are main-sequenceAbsolute magnitude: is bright+10 is dim
54Some Questions for us… Which main-sequence stars are the brightest? Which are the least bright?Which are brighter, giants or dwarfs?Where is the sun?
55HR Diagram Lab Due Wednesday Plot carefully! Scales are not even! Think about what your diagram should look like
56OpenerSuppose you are looking at two stars, one is blue and one is red. Which one is hotter?Where are most stars on the HR diagram (giant, dwarf, or main-sequence)?
57Star deathAll stars will eventually run out of fuel…then they collapseMain sequence, dwarfs, and giants will all eventually “die”This makes sense, if they’re using nuclear fusion (H to He) eventually they’ll run out of H!
58Black Holes What do black holes look like??? Black holes: incredibly small, but EXTREMELY denseThey are old stars (used to be supergiants)So they have a lot of mass in a little areaRemember more mass means more gravity, so these have a lot of gravityEven light can’t escape the gravity of a black hole
59Life, the Universe, and Everything Galaxies: groups of stars, dust, and gasesWhat could hold them together??Gravity!Our sun is within one of the spiral arms of the Milky Way galaxy
60Life, the Universe, and Everything The Big Bang Theory says the Universe began 13.7 billion years ago with a violent explosion.This would explain why the universe is expandingThink of a balloon with a bunch of dots on the outside being blown up…the dots would continually separate from each other. Or think of baking raison bread, the same thing would happen.Cosmic background radiation supports this theoryCosmic waves are faint radio signals coming from every direction in space
61Quick Review What will happen at the end of a stars life? Where is our sun? (in which galaxy, and in what part?)According to the big bang theory, how old is the universe?
62Assignment Finish the worksheet/lab we started yesterday Remember to use a ruler to help guide you!Ask for help!!!When you are done, there are a few questions about the diagram. You’ll need to refer to your notes for this.
63OpenerQuick Write: Again, 60 seconds to spend on the following prompt. Do your best, compete against yourself! Try to beat your old score, but don’t sacrifice quality!Also, reminder that our labs are due today! (on the HR diagram)
64OpenerPrompt: Using definitions, examples, and/or analogies, compare transverse waves to compression waves.Don’t forget the lab is due today! You can turn it in near the end of class.
65Lab QuestionsAre the nearest stars to us necessarily the brightest? How do we know?Why did we not see any white dwarfs on our table?Why is Betelguese so bright, when it’s a cool, distant star?
66Review1. Draw a quick sketch of an HR diagram, labeling the three groups of stars. Label each axis appropriately (you don’t need a scale)
67Review2. Briefly describe how the solar system formed (what did it start with, how did the process go)
68Review3. Draw the picture below, and put as many of the different types of electromagnetic waves as you can remember on it.Short wavelength (λ)Long wavelength (λ)
69ReviewYou can spend the remainder of the time working on the review packetQuiet atmosphere (working individually in your own seat, possibly checking your answers quietly with the person sitting next to you)It will be collected on Friday, but don’t count on having time tomorrow to work!Finish most of it tonight, then you have only a little more to do Thursday night.Highlight/circle the ones you don’t know
70OpenerWhat happens if you increase the frequency of a light wave? (What happens to the wavelength?)What happens if you decrease the frequency?