What is light? Light is that part of the electromagnetic spectrum that, that is seen by your naked eyes.In order for you to understand lighting, I am going to lead you through the basics of light ,that is it terminology.
Why the basics.
I have decided to talk about the basics of light, because I feel it will help you to understand how light is illuminated.
The first step I will walk you through the basic lighting terminology that will help you understand and appreciate light.As I walk you through the basics of lighting, I will define the basic terms used in lighting.
Basic lighting terminology
Here are the basic lighting terms for you.
Luminous
Luminous efficacy
Luminous flux
Light intensity
Candela
Illuminous
Luminous flux
Luminous flux describes the total light power emitted by a light source
Luminous efficacy
Luminous efficacy describes the efficacy of a lamp.It is expressed as a ratio of the luminous flux in lumen and the power used in watts.
Light intensity
An ideal light source radiates its luminous flux evenly in all directions in a room, with its light intensity being equal in all directions. But in practice, this is not so because of the uneven spatial distribution of luminous flux. This is commonly attributed to either lamp design or the manner in which the light is formed.
Candela
This is the unit of light intensity ,as well as a basic unit of lighting engineering from which all other lighting engineering values are derived.
Illuminance
This is a measure of luminous flux density on a surface. Illuminance is expressed as a ratio of luminous flux incident on a surface to the size of the flux.
Colour of light
This is the colour of the light emitted by a lamp. At this point, it is good to mention that the colour of light is categorised into three main groups.
1.Warm white range
2. Neutral white range
3.Daylight white range
Warm white range.
This is the colour range with the coolest temperature below 4000k
Neutral white range
The neutral range colour has a temperature range between 4000k and 5000k
Daylight white range
The lamps in this have a temperature range above 5000k
Colour rending
I know you may be asking as to what is colour rending. I Know you have been to places ,where when the light bulbs are switched on, the colour of the clothes that you are wearing might seem to have changed. This experience is the effect of colour rending. Simply put, colour rending is the ability of a light source to reproduce the surface colours.
Having shown you some of the basic terminology used in lighting,I would like to take you through the type of lamps available on the market.
Types of Lamps
It is important to note that the lamps that I am talking about, are those lamps that use electricity to produce light.Electric light sources are divided into three main category. This grouping is based on how a particular lamp converts electricity into light.Basically, these categories are
Thermal radiator
Discharge lamps
Semi-conductors or LED
Thermal radiators
incandescent bulb
Electric lamps in this group,produce light using an incandescent metal filament.This is a process were by as the temperature increases, the light spectrum of the filament shifts from red heat to warm white light.
Projected features of thermal radiators
Low colour temperature
Excellent colour rendition
Good as a point light source
High luminous which results in its brilliance
Incandescent are excellent dimmers
Do not require additional feature or equipment for starting
They have a low life span
Operation of thermal radiators
In general its good for you to know that all thermal radiators are incandescent lamps.Their basic operation is such that an electric current causes the filament to glow.As the temperature of the light spectrum shifts from red heat to warm white light.
When you dime incandescent lamps,the warm white temperature shits to red heat of the filament. Incandescent lamps generate more thermal radiation than the visible light.
Practical lamps that are thermal radiators
The lamps listed below are practical thermal radiators.
Incandescent lamps
Tungsten lamps
Halogen lamps
Discharge lamps
Lamps in this group generate light either through photo-luminescence or electro-luminescence. This lintels that light is generated using either chemical or electrical processes. Discharge lamps can be divided into low-pressure and high-pressure lamps.
Below is a list of discharge lamps.
Fluorescent lamp
Compact fluorescent lamp
Metal vapour lamp
High-pressure sodium vapour lamp.
Fluorescent lamps
Fluorescent lamps are low pressure discharge lamps.In this lamp, light is emitted from a large surface ,and its light is of diffuse type with low brilliance.
Operation of fluorescent lamps.
For a fluorescent to operate, it needs to have
Electrode
Mercury
Fluorescent coating.
You may be wondering as to how these items or features produce light in fluorescent lamps.Here is how,the electrode produces or releases electrons that collides with mercury atoms.As a result,of this collision the mercury atoms become excited,consequently emitting UV radiation .This UV radiation is converted into visible light by the fluorescence coating.A voltage is used to ignite the lamp.
Properties of a fluorescent lamp.
Fluorescent lamps light colours are
Warm white
Neutral white
Daylight white
For a fluorescent lamp to operate,it needs a ballast and a starter.
Fluorescent lamps consume less power and they have a longer life span.
Compact fluorescent lamps
Compact fluorescent lamps are low-pressure discharge lamps.The operating principle of compact fluorescent lamps is the same like that of an ordinary fluorescent lamp.
Properties of compact fluorescent lamps
They have a high luminous efficacy
They have a long life span
They are shorter in length than ordinary fluorescent lamps,as a result,they can produce focused light.
Compact fluorescent lamps with integrated starters can not be dimmed.
Compact fluorescent lamps are available as straight tubes as well as twisted tubes.
Metal vapour lamps
metal halide
what are metal vapour lamps?These are lamps that produce light by electric arc in a gaseous mixture of vaporised mercury and metal halide.(I know you may be wondering as to what are metal halides,well these are compounds between metals and halogens)The addition of metal halides radiates more light and improves colour.
Properties of metal vapour lamps
Metal vapour lamps have excellent colour rendition.
They have good luminous efficacy
They have a long life span.
Semi-conductor or LED lamps.
LED lamp
You may be wondering as to what are semi-conductors,these are simply engineering materials that are neither conductors nor insulators.
They naturally fall in between conductors and insulators.semiconductors are said to act as insulators at room temperature or temperature below room temperature.
As you increase the temperature of semiconductors above room temperature,their resistance decreases with the increase in temperature until at a certain temperature a semiconductor material becomes a conductor.
Semiconductors were originally used in electronics circuit as indicator lamps.In recent years ,they have been used in general lighting applications were incandescent and fluorescent lamps has been employed.
Characteristics of LED lamps.
LED is a short term for light emitting diode,when you see LED you know that its just a diode, only that its a special diode that can produce light.A diode is made from a semiconductor.
- They do not have filaments,they are made from a cluster of individual LEDs.
- They are instant on lamps
- New model of LED are dimmable
- They are robust,hence they can take bumps without being damaged
- They have a long or longer life span
- LED lamps come in all form of light temperature,that is,warm white.neutral white ,day light as well as in multi-colours.
- LED lamps are not affected by cold weather,on the contrary their light input is increased. This feature makes led lamps suitable for use in cold storage facilities and refrigerated display cases
- LED lamps are sensitive to heat,this does not put them on the disadvantage,because most LED lamps and fixtures are designed with heat sinks.
- LED lamps use 80% less energy than incandescent and halogen lamps
- They use 15% less energy than compact fluorescent lamps.
- when you compare led lamps with other sources of light, the brightness of LED is more than incandescent.This is true when you compare the energy used to produce the brightness of the lamps in lumens LEDs use less energy to produce the same number of lumens as other conventional lamps.All in all LED lamps are excellent energy savers.
- LED lamps do not contain mercury,hence they can be disposed off as normal trush.
- LED lamps cost more than incandescent lamps but their long life span makes them cheaper in the long run.
Should you have any question or contribution you are free to do so.
Leave a Reply