Lecture II Light spectra. The Birth of the Quantum Max Planck –The energy contained in radiation...
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Transcript of Lecture II Light spectra. The Birth of the Quantum Max Planck –The energy contained in radiation...
![Page 1: Lecture II Light spectra. The Birth of the Quantum Max Planck –The energy contained in radiation is related to the frequency of the radiation by the relationship.](https://reader035.fdocuments.net/reader035/viewer/2022062802/56649edb5503460f94bea5e1/html5/thumbnails/1.jpg)
Lecture II
Light spectra
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The Birth of the Quantum• Max Planck
– The energy contained in radiation is related to the frequency of the radiation by the relationship
• n is a positive integer called the quantum number• f is the frequency of the oscillation
– A discreet packet of energy, later to become known as “a photon”
nhfE
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Implications of Planck’s Law
• The energy levels of the molecules must be discreet
• Only transitions by an amount E=hf are allowed
• The implication is that light is discreet or quantised
These quantum levels are known as number states
43210
4hf3hf2hf1hf0
energy n
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Spectroscope
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Three Types of Spectra
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Spectral Analysis of the Elements
Continuous Spectrum: a collection all possible wavelengths/ frequencies of light
Studying the light emitted by an object in order to know something about that object!
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Emission Spectra
Pattern of bright spectral lines produced by an element.
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Absorption Spectra
Pattern of dark spectral lines where light within a number of narrow frequency ranges has been removed.
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HeliumArgon
NeonKrypton
Bright Line Emission Spectra
Hydrogen
Wavelength
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Kirchoff’s Laws• 1st law1st law: A luminous solid or
liquid, or a sufficiently dense gas, emits light of all wavelengths and produces a continuous spectrum of radiation.
• 2nd law2nd law: A low-density hot gas emits light whose spectrum consists of a series of bright emission lines which are characteristic of the chemical composition of the gas.
• 3rd law3rd law: A cool thin gas absorbs certain wavelengths from a continuous spectrum, leaving dark absorption lines in their place superimposed on the continuous spectrum.
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Spectra and BackgroundType of spectrum seen depends on the temperature of the
thin gas relative to the background temperature.
TOP: thin gas cooler than background, absorption lines seen.
BOTTOM: thin gas hotter than background, emission lines seen.
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Studying the Stars:
Analyzing the light from a star can tell us:
1. The composition of the star.2. The relative motion & rotation of the star.3. The star’s temperature.
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Shows limited Range of Light Energies Reaching Earth’s Surface