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What is light?

Light is the relatively small part of the spectrum of electromagnetic radiation that can be perceived by the human eye. The visible light spectrum ranges from 380 nanometres (nm) to around 780 nm. This electromagnetic radiation consists of vibrating packets of energy (quanta) emitted in waves by a light source. The time that light needs to travel from the point of origin to the observer's eye is determined by the speed of light.

In 1850, the French physicist Léon Foucault developed a method of measuring the speed of light using a rotating mirror. It proved highly accurate, establishing that light travels at a speed of 2.98 x 108 m/s. For light travelling in vacuum and air, this is generally rounded to 3 x 108 m/s – i.e. 300,000 kilometres a second.

What are spectral colours?

All colours perceived by the human eye are determined by the wavelength and frequency of visible light. Each wavelength evokes a particular colour. The spectrum of sunlight is continuous, ranging from short-wave violet (starting at approx. 380 nanometres) through blue, blue-green, green, green-yellow, yellow and orange to long-wave red (up to approx. 780 nm). Spectral colours are distinguished by the impression of colour evoked by radiation of a particular wavelength (monochromatic light). For each hue, they are the most intensive colour with the highest saturation.

How is white light created?

Issac Newton discovered that white sunlight can be split into spectral colours. So in a physical sense, "white" light is created by rays of all wavelengths across the spectral range. It is the summation of colours present in the visible part of the electromagnetic spectrum. 

Sunlight is a combination of all the colours of its spectrum. In the case of artificial light sources, white light is produced either by mixing light of different colours or by combining (blue) ultraviolet radiation with phosphorescent (yellow) substances. The phosphor-based method is generally used to produce the light of fluorescent lamps and LEDs. 

Why does white light sometimes look bluish and sometimes reddish?

White light can assume different hues depending on the composition and wavelength of the dominant spectral colour. Where the light emitted by a lamp has a high short-wave blue content, it is perceived as cool. The higher the content of long wave spectral colours, the warmer the impression it makes. The light colour of a lamp is based on colour temperature, which is measured in kelvin (K). The consumer can tell a lamp's light colour from its packaging. Light colours are grouped as follows:

• warm white: < 3,000 K
• neutral white: 3,300 – 5,300 K
• daylight white: > 5,300 K

What is a lux?

Lux (abbreviation: lx) is the unit of measurement for illuminance. It indicates how much light falls on a particular area.

A few examples: sunshine in summer produces as much as 100,000 lux, on an overcast summer's day the figure falls to around 20,000 lux and on the night of a full moon it drops to 0.25 lux. An ordinary candle flame produces approximately 1 lux at a distance of one metre. Instruments for measuring illuminance are available from specialist stockists.

When does light dazzle? And how can glare be avoided?

Glare occurs as a result of excessively high luminance, i.e. the perceived brightness of a luminous or illuminated surface – and can seriously impair visibility. Glare reduces both visual performance and visual comfort.   

A distinction needs to be made between direct glare and indirect, or reflected glare. Apart from excessively bright or incorrectly positioned lamps, for example, glare can also be caused by shiny surfaces (e.g. a glass table-top or computer screen). Glare causes light scatter in the eye, which casts a veiling luminance over the retina (physiological glare) and impairs vision. Even moderate reflection is discomforting and should be avoided.

To guard against glare, attention should be paid to the correct
• shielding
• arrangement
• mounting
• alignment
of lamps and/or luminaires.

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What is the difference between lamps and luminaires?

Originally, the only electrical light source available was the nearly 130 year old "light bulb". It was accommodated in a light fitting that was initially called a lamp. As long ago as the first half of the 20th century, however, the variety of light sources increased and a new definition was required. Since that time, the light source has been called a lamp – and the lighting fitting as a whole, which accommodates the lamp and connects it to the source of electricity, is called a luminaire. Luminaires direct and distribute the light emitted by lamps.

In the case of the LED (light emitting diode), this distinction is largely irrelevant because light generation and optical control are both performed in the diode.

Why will incandescent lamps soon disappear?

The EU has decided to remove incandescent lamps progressively from the market. The reason for this is that incandescent lamps consume too much electricity. They convert only five percent of the energy they consume into light; the rest is dissipated as heat. 

The phase-out of incandescent lamp technology started in 2009 and will be completed in 2012. By then, all incandescent lamps need to conform to at least Energy Efficiency Class C requirements. Because no incandescent lamp meets those requirements, the days of the incandescent "light bulb" are numbered. Halogen lamps can continue to be placed on the market subject to certain restrictions. Far more efficient are energy-saving lamps or LEDs. They deliver a high quality of light and operate much more economically. 

Which lamps can replace an incandescent lamp?

There are three alternatives to the incandescent lamp: energy-saving lamps, LED lamps and halogen lamps. Energy-saving lamps are compact fluorescent lamps, which consume around 80 percent less electricity than incandescent lamps. LED lamps with a screw base are equally efficient direct replacements and have a life of up to 25,000 hours – 25 times longer than an incandescent lamp. 230 V high-voltage halogen lamps deliver a brilliant light and, as energy-optimised (Energy Save) models with an Energy Efficiency Class C rating, consume around 30 percent less electricity than an incandescent lamp. Because they have a much shorter service life than energy saving or LED lamps, they should be used only where short burn times or brilliant light are required. 

More information about the three alternatives is found in the licht.de Incandescent Lamp Special. 

Which other lamps will be removed from the EU market in the coming years?

Other lamps earmarked for removal from the market are used almost exclusively in industry and commerce. They include high-intensity discharge lamps and certain fluorescent lamps. 

For less efficient lamps, the EU has adopted Regulation (EC) No. 245/2009, which sets out new efficiency criteria that will progressively take effect. Under the Regulation, the following types of lamp may no longer be placed on the market: 

• inefficient high-pressure sodium vapour lamps (as of 2012)
• high-pressure mercury vapour lamps (as of 2015)
• inefficient metal halide lamps (as of 2017)

EU Regulation 245/2009 also defines new efficiency criteria for operating equipment and luminaires for the tertiary sector.

More information about this subject is contained in a guide published by the European lighting associations CELMA and ELC. The guide is available for download at www.licht.de. 

How much energy and expense can I save by replacing an incandescent lamp?

Energy-saving lamps and LED lamps require up to 80 percent less energy to generate the same brightness as an incandescent lamp. According to this rule of thumb, a 60 W incandescent lamp can be replaced by:

• an energy-saving lamp, 11 – 12 W (80% energy saving)
• a high-voltage halogen lamp,  42 W (approx. 30% energy saving)
• an LED lamp, approx. 11 – 12 W (80% energy saving).

This also means that anyone today who replaces a 100 W incandescent lamp, for example,  with a similarly bright efficient energy-saving lamp saves an average of 19 euros a year. So by systematically exchanging inefficient incandescent lamps for more less power-hungry lamps, even private consumers can soon cut their electricity bills by well over 100 euros a year. 

When replacing incandescent lamps, what do I need to look out for to ensure that the new lamp will provide a similar light?

With incandescent lamps, it was only necessary to check the shape and the watt rating to find the right replacement. Today, things are different. Watt ratings indicate how much electricity a lamp requires. So anyone wishing to replace an incandescent lamp with a more efficient lamp of the same brightness needs to pay attention to the lumen (lm) rating. It is also important to ensure that the replacement lamp has a similar light colour and a comparable colour rendering index. 

The following lamps are possible replacements for a 60 W incandescent lamp with 710 lumen: 

• Halogen lamps 630 lumen (= 42 W) or 840 lumen (= 53 W)
• Energy-saving lamps 630 lumen (= 11 W) or 850 lumen (= 15 W)
• LED lamps 470 lumen (= 8 W), 650 lumen (= 12 W) or 806 lumen (= 12 W)

Depending on lumen rating, the light of the replacement lamp will thus be a little brighter or dimmer. The relevant lamp ratings are indicated on the packaging. 

Can energy-saving lamps create a homely atmosphere for domestic lighting?

Yes – if the right models are used. Energy-saving lamps are available in many different designs. Make sure that the energy-saving lamp you select fits the luminaire in question; it should not peek over the rim. Another important thing to remember is light colour: energy-saving lamps are available today with warm-white light colours similar to incandescent lamps. Look out for the code 827: The "8" stands for good colour rendering, the "27" for 2,700 kelvin. Warm-white energy-saving lamps are also described as "soft" models. 

Because of their design, energy-saving lamps are always matt, which minimises the risk of glare. Where brilliant, direct light is required – e.g. for chandeliers – halogen lamps or LEDs are the better choice.

Does frequent switching on and off shorten an energy-saving lamp's life?

Good energy-saving lamps handle up to 20,000 switching cycles on average – far more than is normally required for domestic applications. As a basic guideline, high quality lamps with a preheat function are switch-resistant. They can be recognised by the slight startup delay that occurs after they are activated. 

Generally speaking, of course, the more energy an energy-saving lamp saves – i.e. the longer it is switched on – the faster it pays for itself. So an energy saving lamp for around 10,000 switching cycles is generally sufficient for a domestic interior. On the other hand, a more expensive energy-saving lamp should be selected for the stairwell of an apartment building, for example, where maximum brightness needs to be reached fast and a capacity for 20,000 or more switching cycles is required. The number of switching cycles is required to be indicated on the lamp packaging. 

Can energy-saving lamps be dimmed?

The notion that energy-saving lamps cannot be dimmed stems from the early years of energy-saving lamp technology and has long been untrue. Dimmable energy saving lamps are available today in many power ratings and virtually any design. However, energy-saving lamps are not generally compatible with every type of dimmer. As a rule, conventional dimmers – so called "leading edge" dimmers – present no problem. They permit infinite dimming of suitable energy-saving lamps. Some manufacturers also offer energy-saving lamps that can be switched to different brightness levels. Whether an energy-saving lamp can be dimmed needs to be indicated by the manufacturer on the packaging. 

Why do fluorescent lamps flicker when they are switched on?

A fluorescent lamp ignites with the help of a starter only when a sufficiently high current impulse is delivered in the ballast (conventional or low-loss). Because this is rarely the first impulse, the starter tries to ignite the lamp again. A series of such attempts is perceived by the human eye as flickering. Fluorescent lamps start without flickering when operated by an electronic ballast (EB).

Are fluorescent lamps dimmable?

Basically, fluorescent lamps und compact fluorescent lamps are steplessly dimmable. However, this calls for an appropriate electronic ballast (EB) and a pin base connection. Energy-saving lamps with a screw base are not dimmable.

Are fluorescent lamps suitable for short-time operation?

Fluorescent lamps and compact fluorescent lamps (energy-saving lamps) are designed for fairly long operating times between switching. Shorter burning times automatically result in a shorter life. High-quality electronic ballasts (EB) moderate this effect. Fluorescent lamps, for example, have a rated life of around 20,000 hours (16 mm diameter with electronic ballast). However, the light they produce slowly diminishes over that time. There are several reasons for this: lamps become soiled but, above all, they are subject to wear. In both cases, their luminous flux decreases. So it is advisable to replace fluorescent lamps promptly. Loss of light output is considerably reduced by electronic ballasts.

What are LEDs?

LED stands for "light emitting diode". In an LED, electrical energy is converted into light with the help of a semiconductor compound. LEDs are extremely efficient, have a very long life and open up all sorts of new opportunities for lighting. LEDs are used for accent and general lighting. They can be a source of coloured or white light. 

LEDs are available as modules, as LED luminaires and as LED lamps with a screw or plug-in base. Efficient LED lamps can be used as direct replacements for incandescent lamps. They do not quite match the life of LED modules or LED luminaires but they still last for around 25,000 hours, which is 25 times longer than an incandescent lamp.

What are the advantages of LEDs?

LEDs have a very long life of up to 50,000 hours, so they are largely maintenance free. They are already more efficient than energy-saving lamps, have a five times longer life and are constantly being improved. What is more, they are extremely small, robust and easy to regulate. They deliver a highly intense light and emit no IR or UV radiation. 

Are LEDs more expensive than other light sources?

The purchase price of LED lighting equipment is often higher than that of other light sources. But thanks to the high efficiency and long life of LEDs, the initial outlay is quickly recouped because the cost of operating and maintaining the lighting installation is reduced. How that works can be seen from an example in the booklet licht.wissen 17 "LED: The Light of the Future". It shows that the total cost (outlay + operating cost) of an LED corridor lighting installation with four downlights falls below that of a conventional solution with fluorescent lamps in less than four years.

Isn't white LED light cold and uncomfortable?

No, that is a common misconception from the early days of LED technology. Today, LEDs are available in various white light colours. Light colour is indicated by colour temperature expressed in kelvin (K). The spectrum of LED white tones ranges from ≥ 2.700 (= warm white) to 6,500 kelvin (= cold white). Warm white LEDs are generally somewhat less efficient but offer better colour rendering. With special modules, the white light colour of LEDs can even be varied at will – from cool white for better concentration in the morning to warm white light for a cosy atmosphere in the evening.

Can LEDs be dimmed?

Yes, the brightness of LEDs is directly dependent on the strength of the current. So LEDs can be infinitely dimmed down to zero percent light output. Dimming is done via control gear, normally by a method known as pulse width modulation. Here, the light is switched on and off so fast that the flicker is imperceptible to the human eye.

How do halogen lamps work and where do they get their name?

The gas with which the lamps are filled contains halogens (chlorine, bromine, iodine, fluorine). Halogen lamps are thermal radiators – just like conventional incandescent lamps. The light they generate is due to the slow evaporation of a glowing tungsten filament. The evaporated tungsten particles are generally deposited on the inside of the glass enclosure. Halogens slow down this process by carrying the evaporated tungsten particles back to the glowing filament. In doing so, they also increase the luminous flux and life of the halogen lamp.

What shortens the life of halogen lamps?

Halogen lamps are damaged by vibration, overvoltage and temperatures above the permitted maximum.

Why do most incandescent or halogen lamp failures occur the moment a lamp is switched on?

How long incandescent lamps and halogen lamps last depends on the rate of evaporation of the tungsten filament. This is not always uniform over the length of the wire. Thinner points on the filament may also be inherent in the design. They evaporate faster.

When a filament is cold, it has a very low electrical resistance, which causes a high starting current – with correspondingly high temperatures. So when a lamp is switched on, evaporation at the thinnest, weakest point on the filament peaks and the lamp burns out.

Why does the power supply unit for low-voltage halogen lamps stay warm even when the luminaire is switched off?

A transformer is used to lower the mains voltage, normally to 12 V. In the case of many luminaires for low-voltage halogen lamps, the transformer remains connected to the mains even when the lamp is switched off. It continues to consume electricity and therefore generates heat. When a luminaire is not in use, it makes energy-saving sense to disconnect it from the mains.

Why does a transformer sometimes hum?

Transformers generally consist of two coils of wire wound around an iron core. The core is made of thin sheets of iron insulated with a non-conducting material. Transformer hum occurs when magnetic forces cause the iron sheeting to vibrate. Electronic transformers work on a different principle so they never hum.

What is the difference between minimum service life, mean service life and economic life?

Minimum service life is the length of a lamp's life under standard test conditions. Mean service life is the average life of lamps operating under standard-compliant conditions. It indicates the point by which 50 percent of the lamps installed may have failed. Economic life indicates the point at which luminous flux falls below the 80 percent minimum.

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How do you get room lighting right?

Good lighting always starts with careful planning – even in the home. The first question is: How much light is needed for what and where? At this point a distinction is made between three types of lighting:

• background lighting (general lighting) is for orientation;
• zonal lighting (task lighting) provides extra light for areas of the room where specific activities take place;
• mood lighting (accent and decorative lighting) lends structure to the room and creates atmosphere.
• The lighting technologist has a list of quality features that make for good lighting. They determine the choice of lamps and luminaires. Important requirements include adequate brightness (illuminance) and good brightness distribution, glare protection, the right light colour, balanced light and shadow and good colour rendering. More information about lighting design is found under the heading "Lighting for your home".

How many luminaires should be installed in a room?

As a general rule, interior lighting needs to meet lots of requirements. In a living room, for example, someone who is reading requires different lighting than someone watching TV or entertaining guests. A single luminaire can hardly cater for such diverse tasks. Basically speaking, the more luminaires that are installed, the greater the scope for variation in the lighting. It is not possible to put a flat figure on how many luminaires are required; that depends on a range of factors, including:

• the brightness (illuminance) required
• the area of the room
• the number of lamps per luminaire
• the luminous flux of the individual lamps
• the light output ratio of the luminaires
• the reflectance of walls, ceiling and floor

How can reflections be avoided?

Reflections can occur in lots of places, both indoors and out. They are a risk wherever light from lamps, luminaires or other bright surfaces is reflected by shiny surfaces. The problem is that reflections can cause glare. Wet roads, computer monitors, glossy paper and mirrors are frequent sources of reflected glare. To avoid reflections, desks, for example, should be arranged at right angles to the window. Good anti-glare shielding and a favourable arrangement of light sources are also helpful.

What is lighting management?

Lighting management encompasses all systems that go beyond the provision of mere on/off control. Modern lighting management is based on digital data protocols such DALI, control gear and sensors. A lighting management system is made up of various building blocks:

• programmed lighting scenes
• presence-dependent activation/deactivation (presence control)
• daylight-dependent lighting regulation

Apart from greater comfort and convenience, lighting management makes for lower energy consumption because it enables lighting to be more finely tuned to actual needs.

Which luminaires can be mounted on furniture?

Luminaires for direct mounting in or on furniture need to meet certain safety standards. Suitable luminaires display the appropriate fire protection symbols: The letters "F" or "FF" in an inverted triangle (international test standard) broadly correspond to the German "M" and "MM" marks of conformity. Luminaires displaying an "F" or "M" symbol may be mounted on normal flammable materials, e.g. wood with a minimum thickness of 2 mm. In this case, the temperature of the mounting surface and of any materials nearby must not exceed 130° Celsius. In the case of luminaires displaying the "FF" or "MM" symbol, the temperature of mounting surfaces and other surfaces nearby must not rise above 95° Celcius.

Which luminaires can be used outdoors?

The most important criterion here is degree of protection. It is expressed as an IP code ("Ingress Protection") made up of two numerals. The first numeral indicates the degree of protection against solid foreign bodies and dust, the second the degree of waterproofness. For exterior luminaires, the minimum degree of protection required is IP 44. This means they are protected against spraywater and against solid particles with a diameter of more than a millimetre. As a matter of principle, attention to quality pays off when choosing exterior luminaires. Among other things, quality luminaires have the following distinguishing features:

• non-corrosive materials
• ventilation to avoid condensation
• rating plate with marks of conformity such as ENEC or VDE

What needs to be considered when planning lighting for damp interiors?

Bathrooms, saunas and indoor pools are damp interiors – places where water encounters electricity. So where luminairesLuminaires are installed in them, certain safeguards need to be provided. What is more, luminaires should be well protected against the ingress of water and moisture. The indicator for this is the degree of protection.

How long does stairwell lighting need to stay on?

Basically, the lighting needs to stay on as long as it takes the slowest tenant to reach an apartment on the top floor after activating the light at the entrance to the building.

In 1995, Koblenz Higher Regional Court ruled that the owner of a property is derelict in his duty of care if tenants and visitors cannot climb at least two floors at average walking pace without having to operate the light switch a second time (case reference 5 U 324/95).

What can be done to avoid fabrics fading in a shop window?

Light causes photochemical changes, so it is inevitable that fabrics on display will fade. And the problem is not confined to daylight; artificial light sources also emit rays with a shorter or longer wavelength than those in the visible range: ultraviolet (UV) and infrared (IR) radiation.

Depending on degree of lightfastness, merchandise can fade on exposure to light and UVA rays, heat-sensitive materials can dry out, become discoloured or warp under IR radiation.

Basically, the higher the illuminance, the longer the irradiation and the shorter the rays, the greater the bleaching effect. Effective protection against radiation is provided by barrier filters or absorbers.

LEDs emit no UVA or IR radiation. Fluorescent lamps with 830 or 930 light colour have the least bleaching effect. For shop window lighting – and also for museum lighting – data are available about the lightfastness of materials and maximum exposure times.

More information is contained in licht.de publications, which are available for downloading: licht.wissen 06 "Shop Lighting: attractive and efficient" and licht.wissen 18 "Good Lighting for Museums, Galleries and Exhibitions".

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How can electricity savings be made on lighting?

Every household can save energy by using efficient light sources and components and by tailoring consumption to needs. Here are some tips:

• Energy-efficient lamps
Electricity consumption is lowered by the use of energy-efficient lamps. Examples include energy-saving lamps, fluorescent lamps, LEDs and halogen lamps with IRC technology.
• Electronic operating equipment
The use of electronic ballasts (EBs) to operate fluorescent lamps helps save electricity. So does the use of electronic transformers with low voltage halogen lamps. Electronic transformers consume two-thirds less electricity than conventional models and extend the life of the lamps by delivering constant power.
• Avoid "party lighting"
Bright lighting throughout the house wastes a lot of electricity. It is more economical to select illuminance according to needs. Reading, for example, requires only dimmed general lighting and bright directional light on the page.
• Find and deactivate hidden power consumers
Transformers may continue to operate on standby even though lamps are switched off. Whether a transformer keeps working is generally indicated by a faint hum or by the fact that it remains warm after lamps have been switched off. Remote control sockets can be used to disconnect devices that switch to standby mode.
• A great deal of energy is saved by modern electronics
Modern lighting management enhances lighting comfort and saves energy. Motion detectors with photosensors activate lighting only when it is actually needed. Infinitely adjustable digital lighting control with daylight utilisation can be incorporated into a BUS system.

How can I tell whether a lamp is energy-efficient?

How efficiently a lamp operates is revealed on the lamp packaging. The EU energy label shows how economical the lamp is on a scale of A to G. "A" identifies a particularly efficient consumer, "G" an energy waster. The watt rating shows the power required by the lamp and thus gives an indication of the amount of electricity it consumes. To calculate how efficient the lamp is, divide the luminous flux by the watt rating. The resulting variable is known as the luminous efficacy. It indicates how much light a lamp generates from the energy it consumes and is thus a measure of its efficiency. The higher the lumens per watt ratio, the more efficiently the lamp generates light. Here is a comparison: halogen lamps achieve around 20 lumens per watt, energy-saving lamps around 60 lumens per watt.

How much electricity do energy-saving lamps save?

The luminous efficacy of energy-saving lamps is around five times higher than that of conventional incandescent lamps. So an energy-saving lamp requires only around a fifth of the power to produce the same brightness. And less power consumption means lower costs. An energy-saving lamp with an 11 W rating and a life of 10,000 hours, for example, saves around 90 euros in comparison to a conventional incandescent lamp with the same light output (60 W and 1,000 hour life). Energy-saving lamps may cost a little more than conventional incandescent lamps but the initial outlay is quickly recouped – and the environment profits as well.

How much electricity do LEDs save?

The efficiency of LEDs has increased steadily in recent years. In comparison to incandescent lamps, LEDs consume around 80 percent less energy for the same luminous flux. In office lighting, LEDs can lower consumption by 75 percent if obsolete fluorescent lamps are replaced by LEDs with lighting management. In street lighting, the saving potential is 80 percent.

Are there any particularly efficient halogen lamps?

Yes. Low-voltage halogen lamps with infrared coating consume 30 percent less electricity than conventional low-voltage halogen lamps. What is more, the infrared coating doubles the life of the lamp. IRC halogen lamps are also often referred to as "Energy Saving" lamps and have an Energy Efficiency Class C rating.

Are low-voltage halogen lamps also energy-saving lamps?

No. This is a common misconception. "Low voltage" does not mean that less energy is consumed. Low-voltage halogen lamps operate at a low voltage (usually 12 V) but high amperage. Nevertheless, halogen lamps have up to twice the luminous efficacy of conventional incandescent lamps. Always make sure you use energy-optimised (Energy Saving) halogen lamps with an Energy Efficiency Class C rating.

Does switching on a fluorescent lamp consume a disproportionate amount of energy?

No, the additional electricity needed to preheat the electrodes and ignite the lamp is required for only fractions of a second and can be regarded as negligible. The life of fluorescent lamps is established under standardised test conditions. These include a switching rhythm of 165 minutes "on" and 15 minutes "off". Accordingly, fluorescent lamps should not be switched off for periods of less than 15 minutes.

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What are the health implications of light?

Good light facilitates vision, which accounts for 80 percent of all the sensory messages received by our brain. So correct lighting is a major ergonomic consideration, especially at the workplace. At the same time, because light improves perception, it guards against accidents and other risks. Hazards are thus identified earlier and more readily. But light is also an important mental stimulator and generator of a sense of wellbeing. This is because light activates special sensory cells that affect the release of hormones in our body and help regulate our internal clock. Bluish-white light with a high colour temperature, for example, has a stimulating effect, whereas warm-white light colours tend to be soothing. The impact of light on the human organism is a subject of intensive research; the findings have already been harnessed in dynamic lighting and for therapeutic purposes. More detailed information is contained in licht.wissen 19: "Impact of Light on Human Beings".

Is it true that older people need more light?

Yes, a 60-year-old needs about twice as much light as a 20-year-old to experience the same sense of brightness. At the same time, however, older people are more sensitive to glare. Both these facts can be taken into account by a lighting installation with a pronounced indirect component. 

How dangerous is the electromagnetic radiation emitted by energy-saving lamps?

The radiation is caused by the electronic ballasts that are integrated in energy saving lamps. The Federal Office for Radiation Protection in Germany posts this statement on its website: "Radiation resulting from the domestic use of compact fluorescent lamps (energy-saving lamps) for general lighting purposes is not a cause for concern."

Is it harmful to your eyes to look into LED luminaires?

No, a quick glance is no problem because LED luminaires distribute the light emitted by the luminous diodes. However, you should not look directly at any artificial light source for any length of time. 

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Why do fluorescent lamps contain mercury?

Mercury is necessary for the physics of the discharge process that takes place in a fluorescent or compact fluorescent lamp (energy-saving lamp). When the lamp is switched on, a stream of electrons excites the mercury atoms, causing them to emit UV radiation. A phosphor coating on the inside of the tube then transforms that radiation into visible light. Without mercury, the luminous efficacy of the lamp would be two-thirds lower – well below the current state of the art. The mercury content is tiny (a few milligrams). Even so, it is important that the lamps that contain it are properly disposed of and recycled. 

Some energy-saving lamps are labelled "RoHS-compliant". What does that mean?

The acronym RoHS stands for "Restriction of Hazardous Substances" and is a reference to EU Directive 2002/96/EC. This stipulates that energy-saving lamps and electrical equipment should contain no or only minimal amounts of environmental toxins such as lead, cadmium or mercury.

Energy-saving lamps labelled "RoHS-compliant" meet these environmental standards, which are defined in the German Act Governing the Sale, Return and Environmentally Sound Disposal of Electrical and electronic Equipment (ElektroG).

Which lamps need to be disposed of as hazardous waste?

Fluorescent lamps such as energy-saving lamps contain minute amounts of mercury and are classed accordingly as hazardous waste. Their disposal is governed in Germany by the "Act Governing the Sale, Return and Environmentally sound Disposal of Electrical and Electronic Equipment (ElektroG)". It covers the following lamps:
• fluorescent lamps
• compact fluorescent lamps
• discharge lamps
• low-pressure sodium vapour lamps
• luminaires used on commercial or industrial premises 

LEDs also need to be disposed of separately because they contain electronic components. 

For the disposal and recycling of spent lamps in Germany, the lighting industry has established the non-profit enterprise Lightcycle, which operates thousands of disposal points throughout the country. Private individuals can basically dispose of lamps free of charge, normally at municipal disposal points. 

As a matter of principle, private individuals can dispose of such products free of charge, usually at municipal collection points. Incandescent lamps and halogen lamps are not affected. They may be disposed of as household waste.

What should you do if an energy-saving lamps breaks?

Energy-saving lamps often contain tiny amounts of mercury, which is needed for the light generation process. So if an energy-saving lamp breaks, the following rules should be observed:
• Open windows, air the room. 
• Sweep up fragments, preferably with pieces of cardboard or a hand brush, which should be wiped with a damp cloth afterwards.  
• Pick up slivers of glass with moistened paper towels.
• Take broken glass to the disposal point in a sealed plastic bag.

According to the German electrical industry association ZVEI, studies show that it is extremely unlikely that a significant concentration of mercury could be released into the air by damaged energy-saving lamps, even in a worst-case scenario.

What kind of light is not so attractive to insects?

Artificial light attracts insects and can interfere with their natural habits. Insect eyes have a different spectral sensitivity from the human eye. They are less sensitive to light with a high yellow/orange or red content. High-pressure sodium vapour lamps attract insects less because their light appears darker to the insect eye. LED light is also very insect-friendly; it holds little attraction for nocturnal animals. 

More information is contained in the booklet licht.wissen 16 "City Marketing with Light". 

How is light pollution avoided?

Light pollution occurs where radiant light from an exterior lighting installation becomes a source of interference for human beings and wildlife. Sources of light pollution include street lighting, illuminated advertising, floodlighting systems and skybeamers. Professional lighting design helps prevent light pollution and can simultaneously lower energy consumption by establishing how intense and bright the artificial lighting should be and where it should be directed.  Luminaire operating times tailored to requirements also minimise light pollution and cut energy costs.