Candela facts for kids

A candela is a special unit that measures how bright a light source is. It's like saying how strong the light is in a certain direction. The word "candela" comes from the Latin word for "candle."

The candela is one of the seven basic units in the SI system, which is the modern form of the metric system used all over the world. Think of it as a standard way to measure light, just like meters measure length or kilograms measure mass.

What Does a Candela Measure?

A candela measures something called luminous intensity. This sounds complicated, but it just means how much light a source gives off that the human eye can actually see. Not all light is visible to us.

For example, a small flashlight might have a luminous intensity of a few candelas. A car headlight would have many more candelas, meaning it's much brighter. The Sun, which is incredibly bright, has a huge number of candelas!

How is a Candela Measured?

Scientists measure candelas using a specific color of light. This color is a shade of green, with a wavelength of about 555 nanometers. This particular color is chosen because the human eye is most sensitive to it when it's adapted to bright conditions. This means our eyes see this green light very well.

Imagine you are trying to see something in a dimly lit room. Your eyes adjust to the darkness. But when you step outside on a sunny day, your eyes adjust to the bright light. The candela measurement is based on how our eyes see light in those bright conditions.

Why is the Candela Important?

The candela helps us compare different light sources accurately. It's used in many areas, such as:

• Designing LED lights and light bulbs.
• Making sure car headlights are bright enough for safety.
• Creating displays for phones and televisions.
• Setting standards for airport runway lights.

Knowing the candela value helps engineers and designers create lighting that is effective and safe for people to use.

See also

In Spanish: Candela para niños

Images for kids

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  This image shows how light spreads out from a source.