Hello, class! Now, we are going to learn about Low Pressure Sodium Lamps, a type of artificial lighting technology. Let’s get started!

1. What Is a Low Pressure Sodium Lamp?

A Low Pressure Sodium Lamp is a type of gas-discharge lamp that uses sodium in a low-pressure vapor state to produce light. It emits a very distinct yellow-orange glow and is known for its high efficiency in converting electricity into visible light.

2. How Does It Work?

It operates by passing an electric current through a mixture of gases, primarily neon and argon, which heats up and eventually vaporizes the sodium. The sodium atoms become excited and then emit light at a specific wavelength, producing that characteristic yellow-orange light.

• Warm-up Period: It requires a few minutes to reach full brightness as the sodium vaporizes.

• Light Emission: Almost all the light is emitted in a narrow band of the yellow-orange spectrum.

3. Key Components

• Outer Glass Envelope: Protects the inner components and contains an inert gas.

• Discharge Tube: Made of glass or ceramic, containing a small amount of sodium and a starter gas like neon.

• Electrodes: Conduct the electrical current that excites the sodium atoms.

• Ballast: Controls the electrical current and provides the necessary voltage for lamp ignition and operation.

4. Advantages 

Low Pressure Sodium lamps offer several benefits:

• High Luminous Efficacy: They produce a large amount of light per unit of electricity (up to 200 lumens per watt).

• Energy Efficiency: Very low energy consumption compared to other lamp types.

• Long Life Span: Can last over 18,000 hours with proper maintenance.

• Good Performance in Cold Weather: Operates effectively in lower temperatures.

5. Disadvantages

However, they also have limitations:

• Poor Color Rendering: Everything appears yellowish or gray, making it difficult to distinguish colors.

• Bulky Fixtures: LPS lamps require larger and more complex fixtures compared to LED or other modern lighting.

• Warm-up Time: They need time to reach full brightness after being switched on.

• Contains Sodium: Requires careful handling and disposal due to chemical hazards.

6. Common Applications

Because of their high efficiency, they are used mainly in:

• Street Lighting: Excellent for illuminating roads and highways.

• Security Lighting: Used in parking lots and industrial areas.

• Tunnel Lighting: Suitable for providing consistent light in long tunnels.

7. Quick Review Questions

Let’s test your understanding with a few questions:

1. What color light does a Low Pressure Sodium lamp produce? 

2. What is one bad thing about this type of lamp?
   
   
   Ans: Yellow-orange light, Poor color rendering (everything looks yellowish).

Conclusion

In summary, Low Pressure Sodium lamps are highly efficient lighting solutions that emit a distinctive yellow-orange light, making them ideal for outdoor applications like street lighting. While they are very energy-efficient, their poor color rendering limits their use in areas where color discrimination is important. Understanding how these lamps work helps us appreciate the variety of lighting technologies available today.

Thank you for your attention! Let’s move on to the next topic.