Candela

Definition

The candela (cd) is the base unit of luminous intensity in the International System of Units (SI). It is a measure of the amount of light emitted in a particular direction, and it serves as the foundation for other units of light and illumination in the physical world.

5 Must Know Facts For Your Next Test

1. The candela is defined as the luminous intensity of a source that emits monochromatic radiation of frequency 540 × 10^12 hertz and has a radiant intensity of 1/683 watt per steradian.
2. Luminous intensity, measured in candelas, is a key concept in the study of light and illumination, as it quantifies the directional properties of a light source.
3. The candela is used to derive other units of light, such as the lumen, which measures the total amount of light emitted, and the lux, which measures the illuminance or the amount of light falling on a surface.
4. The candela is an important unit in the study of photometry, the measurement of visible light, and is essential for understanding the behavior and properties of light in various applications.
5. The candela is one of the seven base units in the International System of Units (SI), along with the meter, kilogram, second, ampere, kelvin, and mole.

Review Questions

• Explain the relationship between the candela and the other units of light, such as lumens and lux.
  • The candela is the base unit of luminous intensity, which measures the amount of light emitted in a specific direction. The lumen, on the other hand, measures the total amount of light emitted by a source, regardless of direction. The lux, which is the unit of illuminance, measures the amount of light falling on a surface, and it is derived from the lumen and the area of the surface. The candela is the foundation for these other units, as it provides the directional information necessary to understand the behavior and properties of light in various applications.
• Describe the importance of the candela in the study of photometry and its applications.
  • The candela is a crucial unit in the field of photometry, which is the measurement of visible light. Photometry is essential for understanding the behavior and properties of light, and the candela is the foundation for this field. The candela allows for the quantification of the directional properties of a light source, which is essential for applications such as lighting design, photography, and the development of optical devices. Additionally, the candela is used to derive other important units of light, such as the lumen and the lux, which are essential for measuring the total amount of light emitted and the amount of light falling on a surface, respectively. The candela's role in photometry makes it a fundamental unit in the study of light and its applications.
• Analyze the significance of the candela as one of the seven base units in the International System of Units (SI) and its implications for the study of physics.
  • The inclusion of the candela as one of the seven base units in the International System of Units (SI) highlights its importance in the field of physics. As a base unit, the candela provides a standardized and universally accepted way to measure luminous intensity, which is a fundamental property of light. This standardization is crucial for the study of optics, illumination, and various other areas of physics that rely on the behavior and properties of light. The candela's status as a base unit also means that it is used to derive other units, such as the lumen and the lux, which are essential for the study and application of light in various scientific and technological fields. The candela's position as a base unit in the SI system underscores its central role in the study of physics and the understanding of the physical world.

Related terms

Luminous Flux: The total amount of light emitted by a source, measured in lumens (lm).

Luminous Intensity: The amount of light emitted in a specific direction, measured in candelas (cd).

Illuminance: The amount of light falling on a surface, measured in lumens per square meter (lm/m^2) or lux (lx).