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Sodium vapor lamp

A sodium vapor lamp is a type of gas discharge lamp that produces light through the heating and ionization of sodium vapor. These lamps are known for their highly efficient light output and characteristic yellow to orange light . They are widely used in street lighting, industrial lighting, and some scientific applications.

Types of sodium vapor lamps

There are two main types:

1. Low Pressure Sodium (LPS) lamp

  • Light color: Pure yellow (589 nm)
  • Efficiency: Very high (~200 lm/W)
  • Advantages:
    ✔ Extremely energy efficient
    ✔ Long lifespan (up to 18,000 hours)
  • Disadvantages:
    ✖ Poor color rendering (everything appears yellow or black and white)
    ✖ Needs time to reach full strength

2. High Pressure Sodium Lamp (HPS)

  • Light color: Golden yellow to orange (broader spectrum than LPS)
  • Efficiency: High (~100-150 lm/W)
  • Advantages:
    ✔ Better color reproduction than LPS
    ✔ Efficient and powerful
    ✔ More compact lamps than LPS
  • Disadvantages:
    ✖ Still poor color rendering compared to LED
    ✖ Higher operating temperature

How a sodium vapor lamp works

  1. Start-up phase: The lamp contains a small amount of sodium and noble gases (such as neon or argon).
  2. Gas discharge: When switched on, the noble gas ionizes, which helps to heat the sodium.
  3. Sodium Evaporation: As the lamp heats up, the sodium evaporates and begins to emit the characteristic yellow light.
  4. Full light output: After a few minutes the lamp reaches its maximum brightness.

Applications

🚦 Street lighting – Due to its high efficiency and long lifespan.
🏭 Industrial and warehouse lighting – Especially in large spaces where color rendering is less important.
🌿 Greenhouse Lighting – High pressure sodium lamps are used to promote plant growth.
🛑 Tunnel and harbor lighting – Because they can shine well through fog.

Comparison with LED

Although sodium vapor lamps were popular for many years because of their efficiency, they are now increasingly being replaced by LED lighting , which is: ✔ Even more energy efficient
✔ Switches on immediately without warm-up time
✔ Has better color rendering