AST 115 1nd Edition Lecture 9 Outline of Last Lecture I. Johannes Keplera. Properties of an ellipseb. Laws of Planetary MotionII. Galileoa. Telescopic observations and their implicationsIII. Sir Isaac Newtona. Laws of MotionOutline of Current Lecture I. Newton’s Universal Law of Gravitationa. Placing a satellite in Earth’s orbitb. WeightlessnessII. Newton’s revisions to Kepler’s lawsa. 1st and 2nd lawsb. 3rd lawIII. Introduction to Chapter 3: Light and Telescopesa. Properties of a waveb. The Electromagnetic Spectrumc. Particle Nature of Lighti. Waves vs. ParticlesCurrent Lecture Newton’s Universal Law of Gravitation:o Any two objects attract each other with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centersThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.- The arrows of force are the same length (the amount of force is the same for both objects)- d = distance between their centers F=G m1m2d2- Any two objects in the universe are attracted to each other This is a reasonably good approximation as long as there are no other objects in the vicinity.o Three requirements for placing a satellite into Earth’s orbit- Earth’s gravity- Sufficient horizontal velocity (17, 500 mph)- Sufficient altitude (100 miles)o Weightlessness- Astronauts in the Space Station appear to “float” around. Gravity is still acting on the astronauts in the Space Station. In fact,gravity is the only major force acting on them, and they are in “free-fall”. Weightlessness means “lack of support forces or free-fall”. Newton’s revisions to Kepler’s laws:o Newton realized that although the Sun is much more massive than any planet, it is not infinitely more massive.o Newton revised Kepler’s 1st and 2nd laws- Newton stated that Kepler’s 2nd law also expresses an important concept: “Conservation of Angular Momentum”. Conservation of Angular Momentum is like an ice skater spinning (extending their arms to slow themselves down, and bringing theirarms closer to the body in order to speed up)Mass× Velocity × Distance ¿ axis=constantso Newton revised Kepler’s 3rd law:(m1+m2)P2=a3- The units must be: “a” in A.U.s, “P” in years, and m1 in solar masses. Chapter 3: Light and Telescopeso Light behaves like water waves- Properties of a wave: Wavelength = distance between two crests Frequency = number of crests passing an observer per second Speed = wavelength × frequency- Speed of light in a vacuum, “c”299,792,458 km/secorabout 300,000,000 km/sec So, light behaves like water waves, but light doesn’t require any material to support the wave motion.o The Electromagnetic Spectrum- y-ray / X-ray / UV / Light / IR / Radio UV = Ultraviolet rays IR = Infrared radiationo The Particle Nature of Light- Max Planck was the first to discover that light also consists of very small “packets of energy” = photons← greater [Photon Energy] lower →← high [Frequency] low →← short [Wavelength] long →- Waves vs. Particles An experiment designed to detect the wave nature of light does so, and one to detect the particle of nature, does too Reflection: The direction of travel of a light ray is changed by bouncingoff of a surface. Refraction: the direction of travel of a light ray is changed as it passes from one transparent material into
View Full Document
Unlocking...