This page documents an OPTIMADE Unit Definition. See https://schemas.optimade.org/ for more information.

**ID: https://schemas.optimade.org/defs/v1.2/units/si/1967/base/candela**

`candela`

**Unit name:** candela

**Latin symbol:** cd

**Display symbol:** cd

**Description:** The candela is the SI base unit of luminous intensity in a given direction defined in from the radiation of a black body at the temperature of freezing platinum as defined at the 9th CGPM meeting in 1948, clarified at the 13th CGPM Meeting in 1967, resolution 5; and implicitly redefined due to the 1967 SI redefinition of the second.

At the 13th CGPM Meeting in 1967, resolution 5 the previous definition from the 9th CGPM meeting in 1948 was rephrased to be more clear: "The candela is the luminous intensity, in the perpendicular direction, of a surface of 1/600000 square metre of a black body at the temperature of freezing platinum under a pressure of 101325 newtons per square metre."

Furthermore, the SI 1967 definition of the candela references:

- the SI 1960 metre (https://schemas.optimade.org/defs/v1.2/units/si/1960/base/metre).
- the SI 1967 derived newton unit (https://schemas.optimade.org/defs/v1.2/units/si/1967/named/newton) equal to kilogram·metre·second⁻², referencing the SI 1960 kilogram (https://schemas.optimade.org/defs/v1.2/units/si/1960/base/kilogram) and metre (https://schemas.optimade.org/defs/v1.2/units/si/1960/base/metre); and the 1967 definition of the second (https://schemas.optimade.org/defs/v1.2/units/si/1967/base/second).

**Resources:**

- Definition at the 13th CGPM meeting (1967)
- Previous definition at the 9th CGPM meeting (1948)
- Wikipedia article describing the unit

**JSON definition:**

```
{
"$id": "https://schemas.optimade.org/defs/v1.2/units/si/1967/base/candela",
"$schema": "https://schemas.optimade.org/meta/v1.2/optimade/physical_unit_definition.json",
"title": "candela",
"symbol": "cd",
"display-symbol": "cd",
"description": "The candela is the SI base unit of luminous intensity in a given direction defined in from the radiation of a black body at the temperature of freezing platinum as defined at the 9th CGPM meeting in 1948, clarified at the 13th CGPM Meeting in 1967, resolution 5; and implicitly redefined due to the 1967 SI redefinition of the second.\n\nAt the 13th CGPM Meeting in 1967, resolution 5 the previous definition from the 9th CGPM meeting in 1948 was rephrased to be more clear: \"The candela is the luminous intensity, in the perpendicular direction, of a surface of 1/600000 square metre of a black body at the temperature of freezing platinum under a pressure of 101325 newtons per square metre.\"\n\nFurthermore, the SI 1967 definition of the candela references:\n\n- the SI 1960 metre (https://schemas.optimade.org/defs/v1.2/units/si/1960/base/metre).\n- the SI 1967 derived newton unit (https://schemas.optimade.org/defs/v1.2/units/si/1967/named/newton) equal to kilogram\u00b7metre\u00b7second\u207b\u00b2, referencing the SI 1960 kilogram (https://schemas.optimade.org/defs/v1.2/units/si/1960/base/kilogram) and metre (https://schemas.optimade.org/defs/v1.2/units/si/1960/base/metre); and the 1967 definition of the second (https://schemas.optimade.org/defs/v1.2/units/si/1967/base/second).",
"resources": [
{
"relation": "Definition at the 13th CGPM meeting (1967)",
"resource-id": "https://www.bipm.org/en/committees/cg/cgpm/13-1967/resolution-5"
},
{
"relation": "Previous definition at the 9th CGPM meeting (1948)",
"resource-id": "https://www.bipm.org/en/committees/cg/cgpm/9-1948"
},
{
"relation": "Wikipedia article describing the unit",
"resource-id": "https://en.wikipedia.org/wiki/Candela"
}
],
"standard": {
"name": "si",
"year": 1967,
"category": "base",
"symbol": "cd"
},
"x-optimade-definition": {
"label": "candela_si_1967_base",
"kind": "unit",
"format": "1.2",
"version": "1.2.0",
"name": "candela"
}
}
```