This animation illustrates the process of photodissociation of water. When an extreme ultraviolet (EUV) photon strikes a water molecule (H₂O) , it photodissociates the molecule into two separate parts - a hydrogen (H) atom and a hydroxyl radical (OH). The energy from the photon breaks one of the chemical bonds that hold the water molecule together.

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This movie shows how an ultraviolet (UV) photon can break apart a water molecule. When the photon hits the water molecule (H₂O), it adds energy to the molecule. The extra energy breaks one of the bonds between the oxygen atom and a hydrogen atom. The hydrogen atom (H) flies away from the piece that's left, which is called a hydroxyl radical (OH).

This is called photodissociation.

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This movie shows how ultraviolet "light" can break apart a molecule. You need the latest version of the Flash player to see this movie.

Photons are little bits of light. Photons carry energy.

When a photon hits a water molecule, it adds energy to the molecule. The molecule has chemical bonds (they work a bit like stretchy rubber bands!) holding its atoms together. Sometimes the energy from the photon breaks the bond between the oxygen atom and one of the hydrogen atoms. The hydrogen atom flies off! All that's left is the piece with one hydrogen and one oxygen (OH). The OH piece is called a hydroxyl radical.

When a photon knocks an atom out of a molecule, it is called photodissociation.

Photons of ultraviolet (UV) light carry more energy than photons of visible light carry. It takes high-energy UV photons to break water apart!