self-darkening sunglasses a reversible chemical reaction
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Self-Darkening SunglassesSelf-Darkening Sunglasses
A Reversible Chemical ReactionA Reversible Chemical Reaction
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Glasses that darken in sunlight andGlasses that darken in sunlight andbecome clear in ordinary room light become clear in ordinary room light
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Example of a ReversibleExample of a ReversibleChemical ReactionChemical Reaction
• Self-darkening sunglasses use a reversible chemical reaction called “photochromic”
• Photochromic is derived from photo, meaning light, and chromic meaning color
- a change in color with light
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Napthopyran MoleculeNapthopyran MoleculeColorless FormColorless Form
Absorbs only Ultraviolet Light, not Visible Light Absorbs only Ultraviolet Light, not Visible Light
Weak Bond
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Napthopyran MoleculeNapthopyran MoleculeEffect of UV LightEffect of UV Light
UltravioletUltravioletLightLight
UV Light Breaks the Weak BondUV Light Breaks the Weak Bondand Electrons Shift Positionsand Electrons Shift Positions
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Napthopyran MoleculeNapthopyran MoleculeDark Colored FormDark Colored Form
Molecule changes shape afterMolecule changes shape afternew bonds are formednew bonds are formed
New molecule form absorbsNew molecule form absorbslong wavelength visible lightlong wavelength visible light
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Reversible Photochromic ReactionReversible Photochromic Reactionof Napthopyranof Napthopyran
SunlightSunlight
No SunlightNo Sunlight
ColorlessColorlessFormForm
Dark ColoredDark ColoredFormForm