Lighting System

• Lighting accounts for 30 to 40% of the electricity consumed in the Philippines.
• A candela (cd) is the SI unit of luminous intensity — that is, the power emitted by a light source in a particular direction.
• Power generated for lighting creates pollution and greenhouse gas emissions, but it is crucial to the performance of everyday work and play activities.
• The fundamental reasons for providing light in a space are to make the objects in the space visible and to conduct activities that must take place in the space.
• Good architectural lighting provides the right quantity of light, with excellent color rendition and minimal glare.
• Quality lighting has been shown to improve productivity and enhance worker satisfaction.
• Electromagnetic radiation is energy radiated in the form of a wave caused by an electric field interacting with a magnetic field.
• Light is that form of electromagnetic radiation that allows the eye to see.
• Electromagnetic radiation is categorized by wavelength and frequency.
• Electromagnetic radiation is expressed in meters or nanometers (1 nm = 0.000 000 001 meter or one billionth of a meter).
• One inch contains about 25.4 million nanometers.
• Wavelength (λ) is measured as the distance from one peak of one wave to the next wave.
• Frequency is the number of wave cycle per seconds and is expressed in units of hertz (Hz).
• Unimpeded, light travels at the speed of 186 000 miles per second (300 000 000 meters per second) in air or in a vacuum.
• Light tends to travel in a straight-line path unless influenced by a gravitational, magnetic, or some other force.
• The sun and electric lamps are light sources because they transform energy to the visible electromagnetic wavelengths that can be perceived by the human eye.
• Visible light is that part of electromagnetic radiation spectrum capable of exciting the retina and ultimately producing a visual sensation; it is the wavelengths of electromagnetic radiation to which the human eye is sensitive.
• Visible light wavelengths range from about 380 nm to about 750 nm.
• Beyond this range is darkness.
• Although the eye may be exposed to many other wavelengths of radiant energy, they are not capable of initiating responses in the eye.
• Illuminance is the amount of light incident on (striking) a surface.
• Luminance is the amount of light leaving an object.
• The visual system perceives luminance, not illuminance; that is, the eye sees visible light leaving the object, not the light arriving at (incident on) the object.
• When light strikes a surface, the surface is illuminated.
• Compact Fluorescent Lamp (CFL) and Low Pressure Sodium Lamp are examples of high-pressure lamps.
• A bulb is the glass portion of a lamp that encloses and protects the working parts of the light source, whereas a lamp is a source of light.
• When the electric current is passed through the thin metal filament, the filament is heated, glows, and produces light.
• A lamp is a device that generates light.
• Incandescent lamps work on the principle of incandescence, which produces light by heat.
• A luminaire is a complete lighting unit, which consists of a lamp (or lamps), lamp socket(s), any lenses, refractors, or louvers, any ballast (or ballasts), and the housing.
• The rated life of a lamp is its median life expectancy, expressed in hours.
• Efficacy is a measure of how much light a light source produces for the energy put in to it, normally expressed in lm/W (lumens per watt).
• Absorptance (α) is the ratio of the light absorbed versus the light striking the surface.
• A light fixture is the luminaire less the lamp(s), including the structural parts of a luminaire such as any lenses, mounting supports, wiring, and ballasts, but does not include the lamps.
• Luminous flux is the measure of the perceived power of light expressed in lumens (lm).
• Gas-Discharge Lamps are typically filled with a noble gas (argon, neon, krypton and xenon) or a mixture of these gases.
• Low-pressure lamps have working pressure much less than atmospheric pressure.
• High-pressure lamps have a discharge that takes place in gas under slightly less to greater than atmospheric pressure.
• Fluorescent lamps, Low Pressure Sodium Lamp (LPS), and Neon lighting are examples of low-pressure lamps.
• Gas-Discharge Lamps are a family of artificial light sources that emit light by sending an electrical discharge through an ionised gas, i.e. plasma.