concepts week 8 notes
concepts week 8 notes SCMH 1010 - 002
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SCMH 1010 - 002
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This 7 page Class Notes was uploaded by kmb0095 on Friday March 4, 2016. The Class Notes belongs to SCMH 1010 - 002 at Auburn University taught by Allen Lee Landers in Spring 2016. Since its upload, it has received 31 views. For similar materials see Concepts of Science in Science at Auburn University.
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Date Created: 03/04/16
Week 8 2/29/16 A wave having a frequency of 10 Hz means which of the following? 1 wave goes up and down 10 times every second The Two Kinds of Waves: o Transverse Motion is perpendicular to wave direction AM/Short wave radio transmission o Longitudinal Motion is same direction as wave FM radio A long, taut string on a guitar is plucked. The wave that travel down its length is: transverse Technology o Amplitude Modulated (AM) o Frequency Modulated (FM) Which of the following is an observation we can make about pipes in a pipe organ? o The length of the pipe is inversely proportional to the frequency of the sound it produces Interference o Constructive Interference—additive If you have 2 different waves, each 1 inch, and the crests of the waves move together, the result is a 2-inch wave Act together o Destructive Interference—subtractive If crest of one wave lines up with trough of another wave, the result is 0 amplitude Cancellation The Electromagnetic Wave o Maxwell Light is a wave of electromagnetic field Electromagnetic waves change, which creates another electromagnetic wave which changes, and creates another electromagnetic wave, etc. o Michelson There are mediums that let waves propagate Light has no medium The Anatomy of the Electromagnetic Wave o Point A—maximum strength but decreasing o Point B—minimum strength but increasing o Electromagnetic waves continue through internal mechanisms and transfer energy as they travel Light and the Energy of Electromagnetic Waves o Speed of light All electromagnetic waves have same velocity c = 30,000 km/s o Energy Higher frequency = blue color Lower frequency = red color Doppler Effect o Wave motion is independent of its source o If source moves, frequency appears to change o Frequency can change if the source or the receiver move o High pitch to low pitch as it moves away from you The Doppler Effect is NOT observed where the following occurs: both the observer and the source are moving at the same velocity Transmission—wave passes through matter Absorption—wave and energy absorbed Scattering—waves absorbed and reemitted o Diffuse scattering o Reflection Refraction—bending of the light wave 3/2/16 Electromagnetic Spectrum o Maxwell’s equations Predicted more waves o Hertz Radio waves Range: kilohertz to hundreds of megahertz Longest waves Microwaves Range: 1mm – 1m Infared radiation Range: 1mm – 1micrometer () All warm objects emit radiation Visible light Range: 700nm – 400nm Colors o Slices of electromagnetic spectrum Ex) Black & blue or white & gold dress Human color perception is dependent upon the interaction of all receptor cells with light, and this combination results in nearly trichromic stimulation Ultraviolet radiation Range: 400nm – 100 nm Shorter wavelength = more energy o Damage to cells Fluorescence X ray and Gamma rays X rays o Range: 100nm – 0.1nm o High-frequency o Medicine Gamma rays -10 -12 o 0.1nm (10 m) – 10 m o highest frequency o medicine o astronomy 3/4/16 Ch.8 The Atom great idea: all of the matter around us is made of atoms, the chemical building blocks of our world the smallest pieces o Democritus (Greek, ca. 460 BC – ca. 370 BC) o Cut matter to reach the smallest piece Called “the atom” or “uncuttable” Elements o John Dalton (English, 1766-1844) Father of modern atomic theory Cannot break down elements Elements composed of atoms Ex) water molecule is 1 oxygen atom and 2 hydrogen atoms Are atoms real? o Evidence for the reality of atoms Behavior of a gas Ideal of gas equation Change the pressure/volume of gas, temp changes accordingly All comes about from the motion of individual particles Bernoulli (Dutch-Swiss, 1700-1782) o Atoms have mass and velocity and thus kinetic energy o Decreasing volume increases pressure o Increasing temp increases pressure Chemical combinations Dalton discovered the law of definite proportions o Elements combine in a specific ratio of weights Ex) water is 8-parts oxygen to 1-part hydrogen (in weights) o Ratio of weights is a small whole number Ex) 12 lbs carbon can combine with either 16 lbs or 32 lbs of oxygen, but not with 24 lbs of oxygen o Implication: some units of elements are fundamentally indivisible Radioactivity Radioactive carbon to figure out the cycle for chlorophyll (carbon dioxide to oxygen for plants) Madame Curie Discovered in 1896 Phosphors flash when hit by radiation 1903 demonstration of the twinkling caused by this effect Brownian motion Einstein Motion due to individual particles Without those, you wouldn’t see those movements in fluid Erratic, jiggling, motion o Pollen grains suspended in water X-ray crystallography Freeze proteins, shoot X-rays at them to figure out the structure of proteins Used for medical uses Atomic-scare microscopy Actually see individual molecules/atoms The structure of an atom o Joseph Thomson Identified electron (1897) Negatively charged, smaller & lighter than the smallest atom Said atoms are NOT fundamental building blocks, but are made up of smaller more fundamental particles Basically, atoms are the smallest thing that make a thing a thing If you get smaller than an atom, its still stuff (electrons) o The atomic nucleus Ernest Rutherford Determined atomic structure o Atom has a nucleus at center surrounded by electrons Later discoveries found nucleus is composed of protons and neutrons Problems with Rutherford’s model of the atom o Why? Object in circular orbit is accelerating Accelerated electrical charge emits electromagnetic radiation Electrons giving off energy while orbitings Result: electrons spin towards nucleus and eventually atom ceases to exist o Rutherford atom exists <1 min. The nuclear regulatory commission o Logo: highly stylized atomic model The Bohr Atom o First working model of atom o Energy levels for electrons Specific distances from nucleus Electrons exist with no radiation Electrons cannot exist between allowed distances (energy levels) o Energy in Bohr Atom Energy required to leave ground state Absorb proton Heat o Increases collisions Photons: particles of light o Photon absorbed Used to move electron to a higher energy state o Photon emitted as electron moves to lower energy state o Quantum leap or jump – electron disappears from original location and reappears in final location – NEVER at positions in between Spectroscopy o Atoms emit and absorb different photons o Depends on differences between energy levels o Each atom has distinct set of photons o Spectrum All photons emitted by an atom Used for identification o Glass prism The science of life o Spectra of life’s chemical reactions Used to determine how enzymes work Used to identify pollutants emitted from automobile exhaust pipes Technology o Lasers Produce a beam of light