Lecture10 Spectra - Blackbody absorb all of the incident...

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Blackbody absorb all of the incident light, and emits light over a continuous wavelength range. This is the spectrum of a light bulb or Sun at its surface
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Solar Spectrum: thousands of dark absorption lines produced by the gases between Sun and Earth
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Continuous Spectrum Emission Line Spectrum Absorption Line Spectrum Most astronomical sources have spectra like this:
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Why are there different kinds of spectra?
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All matter is made up of various chemical elements such as hydrogen, iron, gold. Each chemical element is made from a different type of atom . What is matter? Appendix F Organized based on atomic number and electronic configuration
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Atoms All matter is composed of tiny particles = atoms Atoms are composed of protons , neutrons , and electrons . protons = + electrons = - neutrons = neutral Mostly empty space!
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Atomic Terminology Atomic Number: # protons in a nucleus Atomic Mass Number: # protons+neutrons
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Which of the following best describes the fundamental difference between two chemical elements (for example oxygen and carbon)? A. They have different names. B. They have different numbers of protons in their nucleus. C. They have different number of electrons. D. They have different atomic mass number. Survey Question
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Which of the following best describes the fundamental difference between two chemical elements (for example oxygen and carbon)? A. They have different names. B. They have different numbers of protons in their nucleus. C. They have different number of electrons. D. They have different atomic mass number. Survey Question Number of protons defines an element
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Atomic Energy Levels The Bohr atomic model (1913) - small dense nucleus The electrons orbiting a nucleus can only sit in particular orbits / energy levels. Each chemical element has its own unique set of energy levels. Niels Bohr and Albert Einstein discussing quantum theory in December 1925
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Atomic Energy Levels Atoms have discrete energy levels. Electrons can only have specific amounts of energy. The lowest energy level is the ground state (zero energy). The other levels are called excited states . States are closer together at higher levels (less energy difference). Distance between levels indicates energy difference.
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Why do emission/absorption happen? Energy Levels H atom model
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For an atom to become less excited it must A. get dimmer. B. absorb a photon. C. emit a photon. D. produce a continuous spectrum. Survey Question
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For an atom to become less excited it must A. get dimmer. B. absorb a photon. C. emit a photon. D. produce a continuous spectrum. Survey Question
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Photons are emitted from an atom when an electron moves from a higher energy level to a lower energy level
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If an atom’s electron jumps from the n=4 energy level to the n=1 level, the atom has _____ energy than/as before.
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