Master this deck with 21 terms through effective study methods.
Generated from uploaded pdf
Radiance is the measure of the amount of light that passes through or is emitted from a particular area, and falls within a given solid angle in a specified direction. It is expressed in watts per square meter per steradian (W/m²·sr).
Radiant intensity (I) is calculated by dividing the total power output (Φ) of the light source by the solid angle (Ω) over which the power is emitted. The formula is I = Φ / Ω, where Ω is measured in steradians.
Radiant flux (Φ) is the total amount of radiant energy emitted by a source per unit time. When considering a surface area, the flux per unit area is known as irradiance (E), which is calculated as E = Φ / A, where A is the area.
The solid angle is a three-dimensional angle that quantifies the amount of the field of view from a particular point. It is crucial in photometry as it helps in determining how light is distributed in space and is measured in steradians.
Irradiance decreases with the square of the distance from the light source due to the inverse square law. This means that if the distance from the source is doubled, the irradiance is reduced to one-fourth of its original value.
The area of a sphere is calculated using the formula A = 4πr², where r is the radius of the sphere. This is important in photometry for understanding how light spreads out from a point source.
Luminous flux refers to the measure of the perceived power of light, weighted by the sensitivity of the human eye to different wavelengths, and is measured in lumens (lm). Radiant flux, on the other hand, measures the total power of electromagnetic radiation, regardless of wavelength, and is measured in watts (W).
The angle of incidence affects the amount of light that is reflected or transmitted at a surface. According to the cosine law, the intensity of light received by a surface decreases as the angle of incidence increases.
Luminous efficacy is defined as the ratio of luminous flux (in lumens) to the power consumed (in watts). It indicates how effectively a light source converts electrical energy into visible light and is expressed in lumens per watt (lm/W).
The sensitivity of the human eye varies with wavelength due to the photopic and scotopic vision systems. Photopic vision (daylight) is more sensitive to green light, while scotopic vision (low light) is more sensitive to blue-green light.
A lux meter is an instrument used to measure illuminance, which is the amount of luminous flux per unit area. It helps in assessing lighting conditions in various environments to ensure adequate illumination for tasks.
Luminous intensity is the amount of light emitted by a source in a particular direction per unit solid angle. It is measured in candelas (cd) and is a key parameter in characterizing the performance of light sources.
A point source is an idealized light source that emits light uniformly in all directions from a single point. This concept simplifies calculations in photometry, allowing for the application of the inverse square law and other principles.
Flux density refers to the amount of radiant or luminous flux received per unit area. It is crucial for understanding how much light is available for illumination on a surface and is measured in watts per square meter (W/m²) or lumens per square meter (lm/m²).
Direct light comes straight from a light source without being scattered, while diffuse light is scattered by surfaces or particles in the environment, resulting in a softer and more uniform illumination.
Luminous efficiency measures how effectively a light source converts electrical energy into visible light. Higher luminous efficiency indicates less energy wasted as heat and more light produced, which is crucial for energy conservation.
Photometric measurements are essential in designing lighting systems as they provide data on light output, distribution, and intensity, allowing designers to create effective and efficient lighting solutions for various applications.
Surface reflectance affects how light is distributed in a space. High reflectance surfaces can enhance illumination by bouncing light around, while low reflectance surfaces may absorb more light, requiring more powerful sources to achieve desired brightness.
LEDs differ from traditional light sources in that they have higher luminous efficacy, longer lifespans, and can emit light in specific colors without the need for filters. They also have directional light output, which can reduce the need for reflectors.
Color temperature describes the appearance of light emitted by a source, measured in Kelvin (K). It indicates whether the light appears warm (lower temperatures) or cool (higher temperatures), influencing the mood and functionality of a space.
Different light sources can affect visual comfort by influencing glare, contrast, and color rendering. Proper selection of light sources is essential to create environments that minimize eye strain and enhance visual performance.