Astronomy section 3

12345678910111213141516171819202122
Across
  1. 5. -A single strontium atom suspended in an electric field
  2. 7. -Reflection is when light bounces off the surface of matter-The coherence (quality) of the reflection depends on the surface smoothness.-Smooth surfaces create coherent reflections, rough surfaces create incoherent reflections.
  3. 9. -Light that loses wavelengths by passing through matter is an absorption spectrum.-Missing colors indicate those that were absorbed by the material.-This is a sensitive technique to measure amounts of material
  4. 13. -Light has wave-particle duality: it can be a wave or a particle. In fact, it can quickly switch from a wave to a particle and vice versa.-All matter has wave-particle duality, but only tiny objects like protons and electrons exhibit this property.-Our measurements affect wave-particle duality. Measure frequency to observe a wave, measure position to observe a particle
  5. 14. -Lightis an oscillating electromagnetic wave. But it also interacts with matter like a particle in the photoelectric effect.-We even call particles of light photons. Is light a wave or a particle?
  6. 17. -Wavelength is the distance a wave travels between peaks. -Frequency and wavelength are inversely proportional; as one increases, the other decreases. -The multiplication of frequency and wavelength is the speed of light
  7. 20. Transmission is when light passes through matter.This process is usually wavelength-dependent. Glass, which transmits all colors roughly equal, usually blocks ultraviolet.A sheet of red acrylic transmits red light much more than other colors.
  8. 21. Does an atom have color?-In order for objects to reflect light, they need to be larger than the wavelength of light being reflected.-Atoms have diameters between 1 Å(0.1 nm) and 0.5 nm.-Single atoms can still emit light, but would emit very few photons.-Short answer: no
  9. 22. -Since white light is a combination of colors, it has many frequencies.-A pure white light source has all colors in equal amounts. Most white light sources we observe have more of some colors than others.-Sunlight has different mixtures of colors depending on the time of day, due to interactions with the atmosphere.
Down
  1. 1. -These three properties of light are all related to each other.-As energy increases, frequency increases and wavelength decreases.-Energy and frequency are proportional, energy and wavelength are inversely proportional.
  2. 2. -An atom’s energy is determined by the electron’s orbital levels.-The electron orbitals increase when the atom absorbs light, and decrease when the atom emits light.-Electrons must always be exactly at these orbital levels; they cannot exist between!-A transition typically uses a single photon-The photon’s energy (color) is exactly equal to the energy gap.-Different elements have different energy levels, so the photons absorbed and emitted are specific to each element.-We can identify elements based on their light absorption and emission. This is spectroscopy.
  3. 3. -Light produced by atomic transitions with only a few wavelengths is an emission spectrum.-By exciting a material with light, the composition of the material can be determined.
  4. 4. Light that is not reflected or transmitted by matter is absorbed.Absorption increases the matter’s energy. It may heat up or emit light.Matter that emits light after absorption are fluorescent or phosphorescent
  5. 6. -All objects emit light due to their internal temperature.-Both frequency and intensity increase with temperature. As this object’s temperature increases, the emission peak shifts to the left and up.- These correspond to increased frequency and intensity
  6. 8. -There are three basic types of spectra: continuous, absorption, and emission.-These spectra can be acquired through different methods, and reveal information about the material under study
  7. 10. -Particles within atoms are even smaller! Protons are 10-14 m: this is 10,000 times smaller than an atom.-Electrons are too small to measure, and may be point particles with no size
  8. 11. -Matter can reflect, absorb, transmit, or emit light.-Many interactions involve multiple processes simultaneously.-Studying light from matter helps us understand it. This is spectroscopy.
  9. 12. -Very little of the total EM spectrum is visible to our eyes. -Long wavelength (low frequency) light is low energy.-Short wavelength (high frequency) light is high energy.-Gamma rays have much more energy than radio waves
  10. 15. -light is emitted from an object by temperature is a continuous spectrum-contains all wavelengths, but often some colors will be more intense than others-this can reveal properties like temperature and composition
  11. 16. The rate that light oscillates (frequency) defines its color, if visible. -Fast oscillations are blue, slow oscillations are red
  12. 18. a fundamental way that we interact with matter, especially when far away. matter can reflect, absorb, transmit, and emit light. What is light? -light is an electromagnetic wave, a combination of oscillating electric and magnetic fields-these fields oscillate in both space and time
  13. 19. -How small is a single atom? Its diameter is about 10-10m.-There are over one million atoms across the diameter of a hair.-Ten million atoms would span the bullet points I use on slides