### Electrons 3.notebook

```Electrons 3.notebook
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Physics and the Quantum Mechanical Model
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Physics and the Quantum Mechanical Model
Light
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How are the wavelength and frequency of light related?
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ヒラギノ角ゴLight
The amplitude of a wave is the wave’s height from zero to the crest. ヒラギノ角ゴ
> The wavelength , represented by λ (the Greek letter lambda), is the distance between the crests. Slide of 38 © Copyright Pearson Prentice Hall
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The wavelength and frequency of light are inversely proportional to each other.
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The frequency , represented by ν (the Greek letter nu), is the number of wave cycles to pass a given point per unit of time. ヒラギノ角ゴ
> The SI unit of cycles per second is called a hertz (Hz).
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The product of the frequency and wavelength always equals a constant (c), the speed of light.
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ヒラギノ角ゴLight
According to the wave model, light consists of electromagnetic waves.
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Electromagnetic radiation includes radio waves, microwaves, infrared waves, visible light, ultraviolet waves, X­rays, and gamma rays. >
All electromagnetic waves travel in a vacuum at a speed of 2.998 ⋅ 108 m/s.
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Electrons 3.notebook
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5.3
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When sunlight passes through a prism, the different frequencies separate into a spectrum of colors.
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In the visible spectrum, red light has the longest wavelength and the lowest frequency.
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The electromagnetic spectrum consists of radiation over a broad band of wavelengths.
Sunlight consists of light with a continuous range of wavelengths and frequencies. ヒラギノ角ゴ
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ヒラギノ角ゴAtomic Spectra
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ヒラギノ角ゴAtomic Spectra
Atomic Spectra
What causes atomic emission spectra?
When atoms absorb energy, electrons move into higher energy levels. These electrons then lose energy by emitting light when they return to lower energy levels.
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ヒラギノ角ゴAtomic Spectra
A prism separates light into the colors it contains. When white light passes through a prism, it produces a rainbow of colors.
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ヒラギノ角ゴAtomic Spectra
When light from a helium lamp passes through a prism, discrete lines are produced.
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Electrons 3.notebook
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ヒラギノ角ゴAtomic Spectra
The frequencies of light emitted by an element separate into discrete lines to give the atomic emission spectrum of the element. 5.3
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Mercury
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ヒラギノ角ゴAn Explanation of Atomic Spectra
An Explanation of Atomic Spectra
How are the frequencies of light an atom emits related to changes of electron energies?
Nitrogen
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ヒラギノ角ゴAn Explanation of Atomic 5.3
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Spectra
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ヒラギノ角ゴAn Explanation of Atomic Spectra
In the Bohr model, the lone electron in the hydrogen atom can have only certain specific energies.
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> When the electron has its lowest possible energy, the atom is in its ground state.
The light emitted by an electron moving from a higher to a lower energy level has a frequency directly proportional to the energy change of the electron.
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> Excitation of the electron by absorbing energy raises the atom from the ground state to an excited state.
> A quantum of energy in the form of light is emitted when the electron drops back to a lower energy level.
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Spectra
The three groups of lines in the hydrogen spectrum correspond to the transition of electrons from higher energy levels to lower energy levels. ヒラギノ角ゴ
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ヒラギノ角ゴQuantum Mechanics
Quantum Mechanics
How does quantum mechanics differ from classical mechanics?
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Electrons 3.notebook
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ヒラギノ角ゴQuantum Mechanics
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ヒラギノ角ゴQuantum Mechanics
Today, the wavelike properties of beams of electrons are useful in magnifying objects. The electrons in an electron microscope have much smaller wavelengths than visible light. This allows a much clearer enlarged image of a very small object, such as this mite.
In 1905, Albert Einstein successfully explained experimental data by proposing that light could be described as quanta of energy.
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> The quanta behave as if they were particles.
> Light quanta are called photons.
In 1924, De Broglie developed an equation that predicts that all moving objects have wavelike behavior. Slide of 38 © Copyright Pearson Prentice Hall
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ヒラギノ角ゴQuantum Mechanics
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ヒラギノ角ゴQuantum Mechanics
The Heisenberg uncertainty principle states that it is impossible to know exactly both the velocity and the position of a particle at the same time.
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Classical mechanics adequately describes the motions of bodies much larger than atoms, while quantum mechanics describes the motions of subatomic particles and atoms as waves.
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This limitation is critical in dealing with small particles such as electrons. >
This limitation does not matter for ordinary­sized object such as cars or airplanes.
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