Lighting Flashcards
What is the range of wavelengths for visible light?
Visible light ranges from approximately 380 nm to 780 nm, with the human eye being most sensitive around 555 nm
Define luminous flux and its unit.
Luminous flux is the perceived power of light emitted by a source, adjusted for the human eye’s sensitivity to different wavelengths. Its unit is lumens (lm)
What is illuminance?
Illuminance is the total luminous flux incident on a surface per unit area, measured in lux (lx) or lm/m2
Define luminance and its unit.
Luminance is the measure of luminous intensity per unit area of light traveling in a specific direction, expressed in cd/m² (candela per square meter)
What is the daylight factor?
The daylight factor is the ratio of indoor illuminance to available outdoor illuminance under overcast sky conditions, expressed as a percentage
What is the CIE photopic luminous efficiency function?
It represents the average spectral sensitivity of the human eye to light in photopic (bright light) conditions, peaking at 555 nm
What is the difference between specular and diffuse reflection?
Specular reflection occurs when light reflects in a single direction, like a mirror, while diffuse reflection scatters light in many directions
What is color rendering index (CRI)?
CRI measures how accurately a light source renders the colors of objects compared to a reference source, on a scale from 0 to 100
Define luminous intensity and its unit.
Luminous intensity is the amount of luminous flux emitted per unit solid angle, measured in candela (cd)
What is color temperature?
Color temperature describes the hue of a light source in terms of the temperature (in Kelvin) of an ideal blackbody radiator emitting similar light
What is metamerism?
Metamerism is the phenomenon where colors appear the same under one light source but differ under another due to varying spectral power distributions
What is the difference between adaptation time and luminance?
Adaptation time refers to how quickly the human eye adjusts to changes in light levels, while luminance is the measurable intensity of light from a surface
What is glare, and how is it categorized?
Glare is visual discomfort caused by excessive brightness or contrast. It can be disability glare (reducing visibility) or discomfort glare (causing annoyance)
What is luminous efficacy, and how is it calculated?
Luminous efficacy is the ratio of luminous flux to power consumed, measured in lumens per watt (lm/W)
What are the three parameters of color perception?
Hue, brightness, and saturation
What factors influence visual comfort in lighting design?
Factors include luminance distribution, glare control, color rendering, and appropriate color temperature
What is the threshold contrast?
Threshold contrast is the minimum contrast required for an object to be distinguishable from its background
What is the difference between illuminance and luminance?
Illuminance: The total light falling on a surface, measured in lux (lx).
Luminance: The light emitted or reflected from a surface in a specific direction, measured in candela per square meter (cd/m2)
What is the role of transmissivity in lighting?
Transmissivity refers to the fraction of light that passes through a material, affecting how much light reaches the other side of a surface
What are the three main optical properties of materials in lighting?
Reflectivity, absorptivity, and transmissivity
What is luminous emittance?
Luminous emittance is the amount of luminous flux emitted per unit area from a surface, measured in lm/m2
Define spectral power distribution (SPD)
SPD describes the power emitted by a light source at each wavelength, showing its color characteristics and energy efficiency
What is luminous intensity distribution?
It describes how light is distributed in different directions from a source, often visualized as a photometric solid
What is the difference between correlated color temperature (CCT) and CRI?
CT: Measures the color appearance of light (warm or cool) in Kelvin.
CRI: Measures how accurately a light source renders colors compared to natural light
What is the EN 12464-1 standard’s recommended illuminance for office workstations?
500 lux is the recommended illuminance for office workstations
How does metamerism affect color perception?
Metamerism occurs when two colors appear identical under one light source but different under another due to varying spectral power distributions
What is a photometric curve?
A photometric curve represents the luminous intensity distribution of a light source in a specific plane
What are the key differences between direct, indirect, and diffused lighting?
Direct lighting: Light travels directly to the target.
Indirect lighting: Light reflects off surfaces before reaching the target.
Diffused lighting: Light is scattered evenly in all directions
What is the Unified Glare Rating (UGR)?
UGR quantifies discomfort glare caused by lighting, with values ranging from 10 (no glare) to 30 (very disturbing glare)
How does specular reflection differ from diffuse reflection?
Specular reflection: Light reflects uniformly, like a mirror.
Diffuse reflection: Light scatters in many directions
What is the recommended color temperature for residential lighting?
Around 2700K to 3000K for warm and cozy lighting
What are the three components of the daylight factor?
Sky component: Light directly from the sky.
Externally reflected component: Light reflected from outdoor surfaces.
Internally reflected component: Light reflected from indoor surfaces
How does glare affect workplace productivity?
Glare causes discomfort and visual fatigue, reducing productivity and increasing errors
What is luminous flux maintenance?
Luminous flux maintenance refers to how well a light source retains its brightness over time
What is the relationship between reflectivity (𝜌), absorptivity (𝛼), and transmissivity (𝜏)?
ρ+α+τ=1. These properties describe how light interacts with a surface or material
Define photometric solid.
A photometric solid is a 3D representation of the luminous intensity distribution of a light source in all directions
What is a Lambertian surface?
A Lambertian surface is a perfectly diffuse reflector, scattering light uniformly in all directions
How does luminous flux differ from radiant flux?
Luminous flux: The visible part of radiant flux, adjusted for the human eye’s sensitivity.
Radiant flux: Total electromagnetic radiation emitted by a source, regardless of wavelength
What are the two main types of glare?
Discomfort glare: Causes annoyance or fatigue without reducing visibility.
Disability glare: Reduces visibility due to excessive brightness or contrast
What are the advantages of LED lighting over traditional sources?
Higher luminous efficacy.
Longer lifespan.
Lower energy consumption.
Instant-on capability.
Environmentally friendly (no mercury)
What factors influence the daylight factor in a room?
Size and position of windows.
Reflectance of indoor surfaces.
External obstructions (e.g., trees, buildings).
Orientation of the building
What is the formula for daylight factor?
DaylightFactor(%)=(IndoorIlluminance/OutdoorIlluminance)×1
