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

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

  • 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.

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


blue light

green light

red light

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 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.

Atomic Emission Line Spectra

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

Atomic Absorption Spectra

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

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






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.





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

Example Atomic Emissions




Example Atomic Emissions

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

Mercury Emission

Mercury Metal

Mercury Vapor Lamp