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# AST 111 Test 2

### test 2

When was Newton born? December 25, 1642
Know about Galileo and the experiments that he performed. He learned that falling bodies are accelerated,that the amount of acceleration did not depend on the mass of the object, and that motion was as natural as standing still.
Why is velocity not the same thing as speed Velocity is different because it is a speed with a specific direction
What happens if we apply the same amount of force to objects with different masses more mass = less acceleration
Know the Law of Gravity states that every point mass in the universe attracts every other point mass with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them.
What is an inverse square law? Strength of gravity decreases as the square of the distance increases
Why do we talk about an orbiting space craft as being in Free Fall? They are falling toward earth but never hit earth as they stay in a fixed position above earth which curves away at the same rate as the object free-falls
What is the circular velocity of an object in orbit? 7780 m/s 17,400 mph
What is "r" in the velocity of an object in orbit equation? "r" is the distance from the center of the earth, sun, etc to the satellite.
What is the distance from the center of the Earth to an object in Geosynchronous orbit? 42,230 km
Why do we care about Geosynchronous orbits? ideal for communications and weather satellites, remains fixed above a spot
What are the different kinds of orbits in an inverse-square-law force ellipse, circle, parabola, hyperbola, straight line
Some orbits are closed and some are open, which are open? Hyperbola, Parabola
Know what is meant by an open and closed orbit closed returns object to its starting point, open escapes
What is escape speed? The escape speed is that speed that allows a space craft to just escape from a planet. That does not mean that it has escaped from the gravity of the planet. Just that, if it is traveling at that speed or faster, it will never fall back to the planet.
What does Kepler's Third law look like after Newton worked on it Newton's version of p^2=a^3, but instead of AU, used m, s , kg
Read about the tides. Why is there a tide on the opposite side of the Earth from the Moon? The moon pulls earth away from the ocean on the far side
What are spring tides and neap tides? neap=mild sun-moon spring=strong sun+moond
Earth's gravity strength 10 Earth radii away 1/d^2 = 1/100 as strong
Acceleration of falling objects 9.8 m/s
What is meant by electromagnetic radiation? light
What is meant by the wavelength and frequency of light? wave= distance b/w peaks repped by lambda, frequency= number of waves passing a stationary point repped by greek v
What is an Angstrom? 1/10th of a nanometer, 10^-10m
What is the velocity of light in cm/sec? velocity=3*10^10 cm/s
What is a photon? particle of light
What is meant by the wave-particle duality of light? light acts as both a wave and a particle
What is the relationship between wavelength, frequency, The higher the frequency, the shorter the wavelengths
How does the energy of a photon of light depend on its wavelength amount of energy a photon carries is inversely proportional to its wavelengths (as one goes up, the other goes down)
What kind of light is most energetic, least energetic? gamma ray most energetic, least energetic is radio
What is meant by atmospheric windows? Certain wavelengths penetrate atmosphere: visible light, some radio waves, some infared
What are refracting telescopes? Reflecting telescopes? How do they differ? refracting use a lense, reflecting use a mirror
What is meant by the primary lens or mirror of a telescope? Eyepiece? the main lens, eyepiece is used to magnify the image and make it convenient to view
What is the fundamental difficulty with refracting telescopes? (Chromatic Aberration),short wavelengths bend more than long wavelengths, so two colors have different focuses
How does a telescope form an image Image is upside down
How is your eye like a telescope? eye sees images upside down as well as it is a lense and brain flips it rightside up
What is meant by the focus of a lens or mirror? focus=light from a distant object focused
What is the focal length of a lens or mirror? focal length is the distance from the lens or mirror to the point where parallel rays of light from a very distant object come to a focus
What is an achromatic lens? Does it really cure chromatic aberration or does it just use it? uses it, two components made of two different kinds of class bring them together, but other colors remain slightly out of focus.
Where are the VLT telescopes located? Why? Mountain top, thinner atmosphere to mess with light
What is the light-gathering power of a telescope? On what does it depend? Ability of a telescope to collect light, PAGE 106, it depends on the area of the telescopes primary lens or mirror (bigger= more light-gathering power)
Created by: jwhorto1