Question

The fluorescent tube and neon sign bulbs consists of:
(A) Solid
(B) Liquid
(C) Gas
(D) Plasma

Answer 1

A fluorescent tube is a low-pressure mercury-vapour gas discharge lamp. It uses fluorescence to produce visible light. A mercury vapour is excited by an electric current in the gas. So it produces short-wave ultraviolet light that creates a phosphor coating on the inside of the lamp to glow. A neon lamp is considered a gas discharge lamp. So fluorescent tubes and neon sign bulbs consist of plasma.

Complete step by step answer:
Plasma lamps are a light source. It generates light by exciting plasma inside a closed transparent burner. Such lamps use a noble gas or a mixture of these gases and other materials such as metal halides, sodium, mercury or sulphur.
In modern plasma lamps like neon sign bulbs and the fluorescent tube, a waveguide is used to constrain and focus the electrical field into the plasma. In this process , the gas is ionized, and free electrons, accelerated by the electrical field, collide with gas and metal atoms. So the fluorescent tube and neon sign bulbs consist of plasma.

Hence, the correct option is (D).

Note: The life of the plasma lamps was limited by the magnetron used to generate the microwaves.. However, using solid-state chips to generate RF is currently an order of magnitude more costly than using a magnetron and so only appropriate for high-value lighting.