Substances produce light when they have _________ been __________________. Electric discharge: _________, When electricity passes through a the gas can give off light. Electric current passes through a gas (neon) Gas heats up → Gas gives off light → yellow light Street lights: Sodium – Neon lights: Neon red light – Argon & mercury greenish-blue light – Krypton pale violet light – Helium pink light – Fluorescence: ___________________ Substances produce light when they absorb (invisible light) _________________________________________. and convert it to Electricity hits mercury vapour Mercury produces invisible UV light → UV light hits fluorescent coating on the inside of the tube → Fluorescent convert it into visible light → Very efficient: use ___________ electrical energy for same brightness ___________ last Phosphorescence:
Substances produce light when they have _________ been __________________. Electric discharge: When electricity passes through a _________, the gas can give off light. Electric current passes through a gas (neon) → Gas heats up → Gas gives off light Street lights: Sodium – yellow light Neon lights: Neon – red light Argon & mercury – greenish-blue light Krypton – pale violet light Helium – pink light Fluorescence: Substances produce light when they absorb ___________________ (invisible light) and convert it to _________________________________________. Electricity hits mercury vapour → Mercury produces invisible UV light → UV light hits fluorescent coating on the inside of the tube → Fluorescent convert it into visible light Very efficient: use ___________ electrical energy for same brightness last ___________ Phosphorescence: