Why are most street lights yellow? The truth is not so simple...

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This article was reviewed by Jingjing Xu, PhD in Physical Electronics, Peking University

At the end of a day's work

Dragging my tired body on the way home

Looking at the road dotted by street lamps

The whole city feels exceptionally bright

I am also surrounded by warmth

but

Have you ever thought about

Why do most street lamps emit light?

All yellow

Instead of white?

today

Just to unravel it for everyone

The secret

…

turn out to be

The street lights we see

Most of the installed high pressure sodium lamps

It mainly relies on metallic sodium vapor to emit light

When first opened, it appears white

After some time

It will turn yellow

That's the color of metallic sodium.

In the street lamp industry

Why choose high pressure sodium lamp

There is a reason for this.

First of all, high pressure sodium lamps have a very high luminous efficiency.

An electric light source

Secondly, strong penetration

Even in foggy weather

Everyone can also stay within a certain range on the road

See the road clearly

Furthermore, it consumes less power

High pressure sodium lamps can

Lights up at lower voltage

Very cost-effective to use

Finally, the light is soft

No eye irritation

Can greatly reduce the incidence of traffic accidents

Do you understand now?

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