Question

The fluorescent tubes and neon sign bulbs glow due to the presence of _ _ _ _ _.
(A) charged particles
(B) high voltage
(C) high temperature
(D) colour

Answer 1

Hint: Both the fluorescent tube and neon bulb are examples of the luminescence light source, as ions are produced within the system, leading to the emission of light.

Complete step by step solution:
Both the fluorescent tube and the neon bulb involves the conversion of the electrical energy to produce light. It takes place as follows:
- In the fluorescent tubes, it is filled with inert gases along with mercury vapour under low pressure. It has an inner phosphor coating, which involves the fluorescence process. As the current is passed through the gas, producing UV light which causes the excitation in the inner coating. This leads to the emission of visible light.
- Whereas, in the neon bulbs, at low pressure the neon gases are present in tightly sealed tubes. On passing a high voltage through the electrode on either side of the tube, the gases within the tube ionise, which leads to the emission of coloured light.
In the case of the fluorescent tubes, they generally give white light whereas, in the neon bulbs, the colour of the emitted light is dependent on the gas-filled inside the tube.
Thus, in both cases, the charged particles as they lower down from the excitation to the lower energy level, it gives out light.

Therefore, the fluorescent tubes and neon sign bulbs glow due to the presence of option (A)- charged particles.

Note: These charged particles from the plasma. That is, known as the fourth state of matter. Due to the presence of charged particles (ions and electrons) in nature, they are affected by the applied voltage.