# The Nature or Light and Matter Chapter 4 Survey of Astronomy astro1010-lee.com.

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The Nature or Light and Matter Chapter 4 Survey of Astronomy twlee2016@gmail.com astro1010-lee.com

Measuring the Velocity of Light Distance is the measured path from the light source, to the rotating mirror, to the stationary mirror, back to the rotating mirror and to the observer. Time is the time it takes for the spinning mirror to turn between reflecting angles. The velocity of light = C = D/T = 300,000 km/sec Chapter 4 Survey of Astronomy twlee2016@gmail.com astro1010-lee.com

The Wave Nature of Light Refraction Refraction is a property of a wave that causes it to change direction as it passes through a different medium. The longer wavelengths are bent the least, the short are bent the most. Chapter 4 Survey of Astronomy twlee2016@gmail.com astro1010-lee.com

The Wave Nature of Light Diffraction Diffraction allows the waves to interact with each other, sometimes cancelling and sometime reinforcing. Chapter 4 Survey of Astronomy twlee2016@gmail.com astro1010-lee.com

Electromagnetic Wave The Wave Nature of Light Visible light is part of an electromagnetic spectrum whose waves travel at the velocity of light. All parts of the spectrum have in common that their waves have both a magnetic and an electric component. Chapter 4 Survey of Astronomy twlee2016@gmail.com astro1010-lee.com

Electro-magnetic Spectrum There is no limit to the wavelengths of the electro- magnetic waves from the very short gamma waves to the very long radio waves. The various sections of the spectrum have different names but they have many features in common. Chapter 4 Survey of Astronomy twlee2016@gmail.com astro1010-lee.com

When solids, liquids or gas at high pressure are heated to incandescence and viewed with at spectrograph the results are Continuous Curves of a characteristic shape. These results are also known as Black Body Curves or Thermal Curves Thermal Curves Chapter 4 Survey of Astronomy twlee2016@gmail.com astro1010-lee.com

Wien’s Law [The hotter the bluer] Chapter 4 Survey of Astronomy twlee2016@gmail.com astro1010-lee.com

Stefan-Boltzmann Law [ The hotter the brighter] Chapter 4 Survey of Astronomy twlee2016@gmail.com astro1010-lee.com

Particle Nature of Light Einstein described the second nature of light as a bundle of energy (photon) which was inversely proportional to the wavelength, Chapter 4 Survey of Astronomy twlee2016@gmail.com astro1010-lee.com

Non-Thermal Radiation Spectral lines are images of the entrance slit on the photo plate in each of the colors contained in the original light. Chapter 4 Survey of Astronomy twlee2016@gmail.com astro1010-lee.com

Non-Thermal Radiation Chapter 4 Survey of Astronomy twlee2016@gmail.com astro1010-lee.com

Hydrogen Emission Lines Chapter 4 Survey of Astronomy twlee2016@gmail.com astro1010-lee.com

Bohr Model of an Atom The Niels Bohr model of the atom was a major leap forward in our understanding of atomic structure, but it was not the final answer. Bohr postulated that electron orbits about the nucleus are quantized. Chapter 4 Survey of Astronomy twlee2016@gmail.com astro1010-lee.com

Photon Emission Chapter 4 Survey of Astronomy twlee2016@gmail.com astro1010-lee.com

Photon Absorption Chapter 4 Survey of Astronomy twlee2016@gmail.com astro1010-lee.com

Hydrogen Absorption Lines Chapter 4 Survey of Astronomy twlee2016@gmail.com astro1010-lee.com

Kirchhoff’s Laws Chapter 4 Survey of Astronomy twlee2016@gmail.com astro1010-lee.com

Kirchhoff’s Laws (Schematic) Chapter 4 Survey of Astronomy twlee2016@gmail.com astro1010-lee.com

Photons Produced and absorbed by electron transitions Transitions Movement of electrons between energy levels Energy levels Stable values of energies for electrons Excitation When an electron is in any level except the ground state By collisions between atoms or by absorption of photons Light and Matter Chapter 4 Survey of Astronomy twlee2016@gmail.com astro1010-lee.com

Chapter Four Doppler Effect Chapter 4 Survey of Astronomy twlee2016@gmail.com astro1010-lee.com

Doppler Effect Original Doppler Experiment Doppler used friends with ‘perfect pitch’ to make the measurements. Chapter 4 Survey of Astronomy twlee2016@gmail.com astro1010-lee.com

Doppler Effect Doppler Equation It must be remembered that this equation only measures ‘line of sight’ velocity Chapter 4 Survey of Astronomy twlee2016@gmail.com astro1010-lee.com

End of Chapter 4 Chapter 4 Survey of Astronomy twlee2016@gmail.com astro1010-lee.com

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