Light Emission Spectra
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Light Emission Spectra & The Quantum Mechanical Model. “ The Sun ”. It is important to keep in mind that we can only ‘ see ’ a small fraction of the universe ’ s energy. The Visible light Spectrum. Light is characterized by frequency, or more commonly, by wavelength

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Light Emission Spectra & The Quantum Mechanical Model

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Light emission spectra the quantum mechanical model

Light Emission Spectra

& The Quantum Mechanical Model


Light emission spectra the quantum mechanical model

“The Sun”

It is important to keep in mind that we can only ‘see’ a small fraction of the universe’s energy


Light emission spectra the quantum mechanical model

The Visible light Spectrum

  • Light is characterized by frequency, or more commonly, by wavelength

  • Visible light spans from 400 nm to 700 nm

    • or 0.4 m to 0.7 m; 0.0004 mm to 0.0007 mm, etc.


Light emission spectra the quantum mechanical model

The Visible light Spectrum


Light emission spectra the quantum mechanical model

White light

  • White light is the combination of all wavelengths, with equal representation

    • “red hot” poker has much more red than blue light

    • experiment:red,green, andbluelight bulbs makewhite

    • RGB monitor combines these colors to displaywhite

combined, white light

called additive color combination—works with light sources

wavelength

blue light

green light

red light


Light emission spectra the quantum mechanical model

Additive Colors

  • Red, Green, andBluelight sources can be used to synthesize almost any perceivable color

  • Red+Green= Yellow

  • Red+ Blue= Magenta

  • Green + Blue = Cyan

  • These three dual-source colors become the primary colors for subtraction

    • why? because absence of green is magenta

    • absence ofredis cyan, etc.


Light emission spectra the quantum mechanical model

Light Spectra

White light contain all colors of light

Hot Matter in condensed states (solid or liquid or dense gas) nearly always emits radiation with a continuous spectrum.

called Incandescence

When the atoms are in a condensed state, the electrons can make transitions not only within the energy levels of their own atom, but also between the levels of neighboring atoms.


Light emission spectra the quantum mechanical model

Atomic Emission Line Spectra

Each element has different wavelengths of light given off when its electrons are excited - an atomic finger print


Light emission spectra the quantum mechanical model

Atomic Absorption Spectra

The white light passing through a cool gas can absorb wavelengths of light to create an absence of color.


Light emission spectra the quantum mechanical model

Emission vs. Absorption


Light emission spectra the quantum mechanical model

QMM and electron excitation

The color of light given off depends on the amount of energy absorbed

The larger the atom the more energy can be absorbed, and more excitation lines produced


Light emission spectra the quantum mechanical model

Excitation

E2

Energy

E1

Nucleus

When the electron has its lowest possible energy, the atom is in its ground state.

Excitation of the electron by absorbing energy raises the atom from the ground state to an excited state.


Light emission spectra the quantum mechanical model

Energy

E2

E1

Emission

A quantum of energy in the form of light (photon) is emitted when the electron drops back to a lower energy level.


Light emission spectra the quantum mechanical model

Example Atomic Emissions

Sodium

Helium

Krypton


Light emission spectra the quantum mechanical model

Example Atomic Emissions

Remember that each element has discrete emission lines that can be measured to define their “atomic fingerprint”


Light emission spectra the quantum mechanical model

Mercury Emission

Mercury Metal

Mercury Vapor Lamp


Light emission spectra the quantum mechanical model

Multiple Source Emissions

Pure Mercury


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