The emission of visible and ultraviolet light by atoms is due to the _

• A. melting of atoms from solid state to liquid state.
• B. condensation of atoms from a liquid state to a gas state.
• C. movement of electrons around its orbit within an atom
• D. transition of electrons from a lower energy level to a higher energy level.
• E. transition of electrons from a higher energy level to a lower energy level.

Answer: (D)