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Get Full Access to UNT - PHYS 1062 - Study Guide - Midterm
Get Full Access to UNT - PHYS 1062 - Study Guide - Midterm

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UNT / Physics / PHYS 1062 / ohad shemmer

##### Description: Covers everything possible from Chapters 1 to 9, excluding 3 and 4 since they won't be on the test. I did my absolute best and drew influence from all the sources I could. Hopefully this helps and you don't have to go searching through all your quizzes, homeworks, or resort to reading. Enjoy!
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PHYS 1062 Midterm Study Guide Extensive study guide for March 2018 exam. Ch. 1 - 9.

## in meters how long is a 1 ​Light year​?

Key Terms:

● Red = Key terms

● Orange = Possible Trivia Questions

● Yellow = If you memorize it, you won’t have to math.

● Green = Put here because it was a quiz question and I can’t explain it but I got it right.

● Blue = Formulas

Ch. 1

● Conversions/Units

○ 1 Light year = 9.461x10^15 meters

○ Earth’s Diameter = 12,756 km = 8.5x10^-5 AU

○ Milky Way Diameter = 80,000 light years

○ 1 AU = 150 million km = 93 million miles

○ The sun’s radius is 100 times the size of Earth’s radius.

○ Astronomers do not measure in MILES.

○ 5K = 3 miles.

● The stars that appear the biggest are the brightest We also discuss several other topics like eku chemistry

● Circumpolar stars never leave the horizon. They would make concentric paths. ● Size

○ Supercluster, galaxy, solar system, planet (from biggest to smallest) ● Scientific Notation

## in diameter how big in the Earth?

○ 10^(number of zeroes)

○ EX: 0.0000788 = 7.88x10^-5

● Seasons and Tilts

○ We have seasons because of the Earth’s tilt.

○ In the winter, the sun is above the horizon for less than 12 hours and at low angles, so there’s less concentrated solar heating or sunlight.

● It takes 5.8 minutes for the sunlight to reach Venus.

● It takes 8 minutes for the sunlight to reach Earth.

● It takes 4.2 light years for the sunlight to reach Alpha Centauri

○ Alpha Centauri is the closest star to our sun.

● Earth rotates from west to east. (on the HW question, it’s the sunset line on the right)

● When observing a star for a few hours, it moves from east to west. ○ An overhead star will move through the 15* angle in one hour.

Ch. 2

● Precession = The Earth moves like a top (imagine the one at the end of Inception) ○ Why does this happen? - The Sun and Moon pull on Earth’s equatorial bulge.

## in diameter how big in the Milky Way?

○ It changes the celestial poles, the equinoxes, the solstices, and the celestial equator.

● Greek Letters = Describe the relative brightness within the constellation ○ Alpha - Brightest

○ Beta - Second brightest

● Celestial Sphere = It’s not physically real, but it is still useful.

○ 88 Regions (constellations)

○ Don’t confuse constellations for asterisms.

■ Asterisms are like...The Big Dipper.

○ Horizon

○ North and South Celestial Poles We also discuss several other topics like bul 4310 fiu

○ Celestial Equator

● Milankovitch Hypothesis = Small changes influence Earth’s climate and cause ice ages.

● Magnitude

○ If one star is 100 times brighter than the other, the magnitude difference is 5.

○ 1st Magnitude is very bright. 6th Magnitude, not so much.

○ The higher the number the dimmer the star. (-2.7 vs 2.7)

● Flux

○ Measure of the light energy from a star that hits one square meter in one second.

○ 2.512^(the difference in magnitudes classes)

● The 5 naked-eye and 2 telescopic planets that wander among the stars will always be near the ecliptic.

● It takes the sun 2 minutes to completely set once it touches the horizon.

Ch. 5

● Newton If you want to learn more check out ams 210 stony brook

○ 3 Laws of Motion

■ An object in motion will stay in motion. (or at rest will stay at rest) Unless acted upon.

■ F = ma (Force = Mass*Acceleration)

■ Equal and Opposite Reaction.

● So the amount of force on the Sun by the Earth is the same as the amount on Earth by the Sun.

○ There was a force pulling the Moon to Earth

■ The Moon’s orbital motion has a curved fall.

■ Moon has an acceleration towards Earth

■ The force and acceleration in Newton’s second law must have the same direction.

■ (If there’s a question that has all these answers and another, pick all the above)

■ If the gravity was turned off, the moon would fly off into space in the direction it was facing INSTANTLY.

○ What’s necessary about the force exerted by the Sun (to yield elliptical orbits)

■ The force must be attractive and the force must vary inversely with distance squared.

● Galileo

○ Slowed down time

■ Rolled objects down inclines at low angles. Don't forget about the age old question of What do phagocytes produce to kill bacteria?

○ Worked out the law of inertia (Law #1)

● Force

○ If two planets orbit the sun (Earth and Q), and Q is five AUs away from the sun, Q has 1/25 the force on Earth. The two planets are identical. ○ Why would a hammer and feather land at the same time?

■ No air resistance.

○ Mass Vs. Weight

■ Mass is the amount of matter

■ Weight is the amount of gravitational force you experience.

○ You’re never weightless, just in constant freefall.

● General Relativity

○ Solved the major orbital problem: The excess precession of Mercury’s perihelion.

○ Verified on May 29, 1919 solar eclipse (bending of light by gravity) ○ Explains the following

■ Light bending in the vicinity of massive objects.

■ Time dilation close to massive objects

■ Gravitational redshift.

■ Mercury’s orbit does not follow Newton’s laws precisely.

● Albert Einstein

○ Proposed that gravity is the bending of space-time due to the presence of matter.

● Circular Motion

○ Acceleration of the object is toward the center of motion.

● Escape Velocity

○ If we shrink the Earth’s radius by a factor of 100, but we keep the mass, the escape velocity will increase by a factor of 10.

● If there’s an alien beam question, it’s the speed of light.

● Speed vs. Velocity vs. Acceleration

○ Speed - how fast are you going?

○ Velocity - how fast are you going and WHERE?

○ Acceleration - something changed and we gonna find out what.

● Law of Universal Gravity

○ F = -G (Mm/r)

● Free Fall

○ G = Fgravity/M = Fgravity/m

● Escape Velocity

○ (2GM/r)^(½)

Ch. 6

● Speed of light = Frequency x Wavelength.

● Speed of light = 3x10^8 m/s

● E = hf

● H = 6.626 x 10^-34 J*s is the Planck Constant

● Light cannot be portrayed as a wave and a particle in the same experiment. ● Infrared telescopes are on mountaintops and ultraviolet telescopes are in Earth’s orbit.

○ Infrared blocker, water vapor, is in the lower atmosphere.

○ Primary ultraviolet blocker, ozone, is in the higher atmosphere. ● Infrared telescopes

○ Must be cooled to a low temperature to reduce interfering heat radiation emitted by the telescope.

● Electromagnetic radiation travel in any medium that does not absorb them. ● PURPOSE OF A TELESCOPE

○ To gather light and bring it to a focus.

○ Width matters, not length. (*winky face*)

● Big telescopes (size does matter?) now.

○ They can be made thinner and lighter.

○ Tracking is computer controlled.

○ Reduced effect of the Earth’s atmosphere.

○ (pick all of the above)

○ A = pi (p/2)^2 Surface area of the primary lense.

● Chromatic Aberration

○ Prisms take advantage of it.

○ It’s a big problem for the primary lenses of refracting telescopes

● Resolving Power

○ Limited by a cloudy night.

○ Expressed as “0.5 seconds of arc.”

● Electromagnetic Spectrum

○ Visible and Radio are the most transparent to Earth’s atmosphere. ○ Visible Spectrum

■ ROYGBIV

● Violet’s photons have the greatest energy.

○ X-Ray Telescopes can observe hot gas trapped in galactic clusters better than an infrared telescope.

○ Infrared Telescopes can observe newborn stars in dusty nebulae better than an X-Ray telescope.

○ Rank telescopes designed for the following specific types of electromagnetic waves in order of the minimum altitude at which they would be useful. (least to greatest)

■ Visible

■ Infrared

■ X-Ray

○ Rank telescopes designed for the following specific types of electromagnetic waves in decreasing order of the altitudes at which they would be useful (greatest to least)

■ Ultraviolet

■ Infrared

■ Visible

● Radio Telescopes vs Optical Telescopes (everything radio does best) ○ Find the location of cool hydrogen gas

○ See through dust clouds

○ Detect dark molecular clouds

○ Observe during the day

○ (so pick all of the above)

● Determined exclusively by the diameter of the primary mirror or lens. ○ Light Gathering Power and Resolving Power.

○ Overcomes poor resolving power.

■ It’s poor because the wavelengths are so long.

● It’s about light gathering, not magnifying.

○ Pupils

○ Telescopes.

● If you were to make a telescope using the two lenses (it’ll show you a diagram with two blue and white looking things)

○ One uses top lens for the primary and bottom lens for the eyepiece.

Ch. 7

● Spectral Types

○ Seven Types: OBAFGKM. O is hottest.

○ Red is the lowest surface temperature for a star compared to (Orange, White, Yellow, and Blue)

○ Blue is the color of the hottest stars.

■ Blue star’s emissions peak at shorter wavelengths than red ones. ○ Temperature controls the color of a star.

● Spectral Lines

○ If it’s blueshifted, the radial velocity is directed towards us.

○ If it’s redshifted, the radial velocity is directed away us.

○ Properties of a star that can broaden the width of its spectral lines ■ Rapid rotation of the star

■ High temperature atmosphere

■ High density atmosphere

● Where is the location of the cooler low-density gas that yields the dark line stellar spectra that were studied by Annie Jump Cannon

○ In the star’s lower atmosphere

○ In Earth’s atmosphere

● Continuous

○ Observed when observing radiation from a hot solid or gas under high pressure.

○ Observe from molten lava.

● Absorption

○ Light from a continuous spectrum source passing through a cooler low density gas produces the absorption line spectrum.

○ Observed when observing radiation through a cool gas.

○ Observed if you looked through gases boiling out of molten lava. ● Emission

○ Observed when observing radiation from a hot gas.

● Black Body

○ All stars!

○ Wavelength of maximum intensity that is emitted is inversely proportional to temperature.

○ Amount of electromagnetic energy radiated from every square meter of the surface is proportional to temperature to the fourth power.

● Temperature of a gas is a measure of the

○ Average motion of its atoms

● Atomic Nucleus

○ All the positive charge

○ 99.9% of the mass

○ No electrons

● Ionized atoms = Atoms with more of either electrons or protons than the other ● Stars are mainly hydrogen and helium but they have no lines for hydrogen or helium in their spectrum. Why?

○ The surface temperature is such that the electrons are not at the proper energy levels to produce spectral lines at visible wavelengths.

● The electron making the transition from level 2 to level 3 corresponds to a hydrogen atom absorbing a visible light photon that has a wavelength of 656 nanometers.

○ Determined by the difference in energy between electron energy levels.

Ch. 8

● The Sun

○ Maintains its energy output by fusion of hydrogen nuclei.

○ Magnetic field is responsible for the surface and atmospheric activity. ■ Changes because of the differential rotation of the Sun and

convection beneath the photosphere.

○ Changes in the magnetic field heat the chromosphere and corona to high temperatures.

○ The lower photosphere is hotter than the upper photosphere is responsible for “limb darkening.”

○ Photosphere contains the cooler low-density gas responsible for absorption lines in the Sun’s spectrum

○ Corona is a very hot low-density gas.

○ The layers of the Sun below the photosphere are explored by measuring and modeling the modes of vibration of the Sun’s surface.

○ The general trends in temperature and density from the photosphere to the chromosphere to the corona - Temperature increases and density

decreases.

○ Photosphere is not part of the interior.

● Layers of the Solar Interior Ranking Questions

○ Outermost to innermost

■ Convective Zone

■ Core

○ Increasing temperature (least to greatest)

■ Convective Zone

■ Core

● Solar Prominence

○ Solar Material from the chromosphere following the arches of the sun’s magnetic field

○ Its spectrum reveals that it is much cooler than its surroundings. ○ The shape suggests that it is following the solar magnetic field.

● Solar Flare

○ Eruption of solar material from the photosphere

○ Observed at Visible, Ultraviolet, and X-Ray wavelengths

○ Can bring auroras and communication blackouts.

● Solar Neutrino Problem

○ Solved by the discovery that neutrinos oscillate between three different types.

● Solar Neutrinos

○ Created during nuclear fusion

○ Very low mass

○ Travel very fast

○ Detected in large underground pools of chemicals

○ They’re hard to detect because they move fast, have low mass, and oscillate between three flavors.

● Supergranules and Granules

○ Both due to convection cells in the layers below.

○ The center of a granule is brighter than its edges because the temperature is higher at the center.

● Nuclear Fusion

○ Happens at the core

○ Requires high temperatures because:

■ Protons repel each other

■ Overcoming the Coulomb barrier

■ (it’s the one that says all of these choices)

● Proton-Proton Chain

○ Produced from the neutrinos

○ Head out of the Sun at nearly the speed of light.

● How constant is the Solar constant? How much has the solar constant been observed to vary?

○ About 0.1% , so pretty darn constant.

Ch. 9

● Sun

○ Spectral Type is G2, Luminosity is Main Sequence (V)

○ If a star with the same type has a luminosity of 50 solar luminosities, it must be larger than the sun.

● Luminosity

○ Cool stars can be more luminous than hot stars if the cool star is larger. ○ Supergiants have the lowest density

○ Main Sequence applies the mass-luminosity relation.

○ If a star has ½ the surface temperature of the Sun and is 4 times larger, the star’s luminosity is 1 solar luminosity

○ L = Surface Area (A) * O (that ugly constant) * Temperature in Kelvin (T)^4 ● Distance

○ Parallax Angle of .5 arcseconds = distance of 2 parsecs

○ If a star’s apparent visual magnitude is less than its absolute visual magnitude, the distance to the star is less than 10 parsecs.

○ How to find without parallax angle

■ Spectral Type and Luminosity Class

○ At 10 Parsecs, the apparent magnitude equals the absolute magnitude ● Red Dwarf

○ Most abundant but rarely plotted because they have low luminosity and are hard to detect.

● Magnitude

○ Absolute bolometric magnitude gives the most information about the physical nature of a star.

■ Medium surface temperature stars have the least difference

between absolute visual magnitude and absolute bolometric

magnitude.

● Order of brightness from dimmest to brightest

○ Barnard’s Star

○ Sirius B

○ Sun

○ Canopus

○ Rigel A

● Brightest to Dimmest

○ Antares

○ Polaris

○ Aldebaran A

○ Altair

○ Procyon B

● Hottest to Coolest

○ Aldebaran A

○ Altair

○ Antares

○ Mira

○ Rigel A

d(parsec) = 1/p

Mv is Absolute visual magnitude

Magnitude Distance Formula. 10^(mv-Mv +5)/5 1 Parsec = 3.26 Light Years

1a = Bright Supergiant

1b = SuperGiants

2 = Bright Giants

3 = Giants

4 = Subgiants

5 = Main Sequence

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