🔍 Key Concepts

• Fluorescent lamp operation: how mercury vapor inside the tube produces mostly ultraviolet (UV) radiation, not visible light • Phosphor coating on the inside of the glass tube and how it converts one type of radiation to another • Difference between visible light and invisible ultraviolet light in the electromagnetic spectrum

💭 Think About

• In a bare mercury-vapor discharge without phosphor, what part of the spectrum is mainly produced, and can we see it directly? • What must the phosphor do to make the lamp useful for general illumination that our eyes can see? • Look carefully at figure A: how does the label of the inner coating relate to the argon gas and mercury vapor inside the tube?

✅ Before You Answer

• Be clear on which is invisible (ultraviolet) and which is visible (white light to our eyes) • Confirm whether the coating’s main role is to absorb or block one type of radiation and what type it then emits • Eliminate any options that claim the coating absorbs or emits radiation that is already in the visible range inside the bare tube