the nature or light and matter chapter 4 survey of astronomy [email protected] astro1010-lee.com
TRANSCRIPT
The Nature or Light and Matter
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Measuring the Velocity of LightDistance 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
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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.
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The Wave Nature of Light
Diffraction
Diffraction allows the waves to interact with each other, sometimes cancelling and sometime reinforcing.
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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.
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Electro-magnetic SpectrumThere 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.
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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
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Wien’s Law [The hotter the bluer]
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Stefan-Boltzmann Law [The hotter the brighter]
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Particle Nature of Light
Einstein described the second nature of light as a bundle of energy (photon) which was inversely proportional to the wavelength,
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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.
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Bohr Model of an AtomThe 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.
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PhotonsProduced and absorbed by electron transitions
TransitionsMovement of electrons between energy levels
Energy levelsStable values of energies for electrons
ExcitationWhen an electron is in any level except the ground stateBy collisions between atoms or by absorption of photons
Light and Matter
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Doppler EffectOriginal Doppler Experiment
Doppler used friends with ‘perfect pitch’ to make the measurements.
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Doppler Effect
Doppler Equation
It must be remembered that this equation only measures ‘line of sight’ velocity
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