Physics final

• Before the invention of the telescope, several astronomical phenomena were already known to astronomers. Most of these were from observations of early civilizations such as Egyptians and Babylonians.
• Examples of astronomical phenomena known before the telescope

  • Different phases of the moon
  • Lunar and solar eclipses
  • Diurnal and annual motion of stars
  • Location of the planets Mercury, Venus, Mars, Jupiter, and Saturn
  • Sun rises in the east and sets in the west
  • Location of sunrise and sunset changes in a year
• Copernican Model


  Heliocentric model proposed by Nicolaus Copernicus, showing the Sun as the center of the universe and the planets, including the Earth, orbiting around it. Explains retrograde motion of planets.

  
• Ptolemaic Model


  Geocentric model proposed by Claudius Ptolemy, showing the Earth as the center of the universe and other heavenly bodies revolving around it. Describes the path of planets as circular with epicycles.

  
• Tychonic Model


  Combination of the Copernican and Ptolemaic models, retaining the geocentric model with the Earth at the center, but also showing the planets revolving around the Sun.

  
• Tycho Brahe


  • Provided some of the most accurate observations of astronomical phenomena without the aid of a telescope
  • Discovered a new star in the constellation of Cassiopeia, disproving the idea of an unchanging universe
  • Observed comets, showing the discrepancy in Aristotle's transparent spheres
  • Proposed a model of the solar system that is a mixture of the Ptolemaic and Copernican models
  • His observations of Mars' movements paved the way for the development of Kepler's planetary motion

  
• Kepler's Laws of Planetary Motion

  1. First Law: The shape of the planet's orbit is elliptical, with the Sun as one of its foci

  2. Second Law: A line joining a planet and the Sun sweeps out equal areas during equal intervals of time

  3. Third Law: The square of the orbital period of a planet is directly proportional to the cube of the semi-major axis of its orbit
• Wave motion


  Transfer of energy, not matter, by waves

  
• Wave propagation


  • Waves in water
  • Waves in solids (earthquakes)
  • Waves in gases (sound)

  
• Wave characteristics


  • Wave velocity (speed and direction)
  • Wavelength (λ, distance of one complete wave)
  • Wave amplitude (A, maximum displacement from equilibrium)

  
• Wave frequency (f)


  Number of oscillations or cycles per second, measured in hertz (Hz)

  
• Wave period (T)


  Time it takes the wave to travel one wavelength

  
• Frequency (f) and period (T)


  Inversely proportional
• Wave speed (ν), wavelength (λ), and frequency (f)


  ν = λ × f

  
• Calculating wavelength


  1. Given: wave speed (ν) and frequency (f)

  2. Rearrange equation ν = λ × f to solve for λ

  
• Speed of light (c) = 3.00 x 10^8 m/s
• Dispersion


  • Different wavelengths of light bent at slightly different angles when refracted
  • Causes white light to be dispersed into a spectrum of colors when passing through a prism
• Diffraction


  Bending of waves as they pass through small openings or around corners
• Degree of diffraction


  Depends on wavelength and size of opening/object
• Interference


  Combination of two or more waves resulting in a new waveform

  
• Types of interference


  • Constructive interference (waves reinforce, amplitude increases)
  • Destructive interference (waves cancel, amplitude decreases)

  
• Photon


  Quantum of electromagnetic radiation, a "particle" of light

  
• Photon energy


  Higher frequency light has higher photon energy

  
• Applications of photon energy

  • Blue light has higher energy than red light
  • UV rays have high photon energy and can cause skin damage
• Celestial domain


  The domain of the universe beyond the Earth
• Photoelectric effect


  Emission of electrons from certain metals when exposed to light
• Terrestrial domain


  The domain of the Earth and its movement
• Terrestrial motion


  1. Motion with respect to quality

  2. Motion with respect to quantity

  3. Motion with respect to place
• Photoelectric effect cannot be explained by wave model, but can be explained by photon concept

  
• Diurnal motion


  The daily motion of heavenly bodies such as stars across the Earth's sky

  
• Annual motion


  The yearly motion of the stars and other heavenly bodies as seen from the Earth

  
• Types of light spectra

  • Continuous spectrum
  • Line emission spectrum
  • Line absorption spectrum

  
• Precession of the equinoxes

  The apparent movement of the equinoxes, which takes place about every 26,000 years
• Ancient Greek philosophers already believed that the Earth is spherical
• Wave-particle duality of light

  Light exhibits both wave and particle (photon) properties to explain different phenomena

  
• Philosophers who proposed the spherical Earth

  • Pythagoras
  • Plato
  • Aristotle
  • Eratosthenes

  
• Solving problems

  1. Given: wave speed (ν) and frequency (f), find wavelength (λ)

  2. Given: frequency in MHz, find wavelength

  3. Given: wavelength in nm, find frequency

  
• Evidence for the spherical Earth

  • Different constellations observed when traveling from north to south
  • The horizon moving further away when the observer is at a higher elevation
  • The Earth's curved shadow on the Moon during lunar eclipses

  
• Theory of planetary motion

  Planets move in a perfect circular motion

  
• Sound wave speed = 344 m/s, wavelength = 0.500 m, frequency = 688 Hz