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Why does beta-carotene have a bright yellow colour?

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Isoprenoid Camphor, an isoprenoid compound classified as a terpenoid ketone, is used in incense and certain medicinal compounds. It is a natural substance obtained from the camphor laurel (*Cinnamomum camphora*), a species of evergreen.

Beta-carotene, a member of the isoprenoid series, exhibits a bright colour due to its molecular structure, which contains an extensive system of 11 conjugated pi bonds.1

In organic chemistry, conjugated systems consist of multiple pi bonds separated by single bonds. Electrons within these bonds occupy molecular orbitals that span several atoms, allowing them to absorb energy from light in the visible region of the electromagnetic spectrum. As the number of conjugated pi bonds increases, the molecule absorbs light at longer wavelengths and lower energy levels.12

Because beta-carotene absorbs specific wavelengths of visible light, the light that is transmitted or reflected gives the compound its characteristic bright orange-yellow appearance. This ability to interact with light is a defining feature of chromophores, the parts of a molecule responsible for its colour.12