You see fluorescent lamps everywhere -- in offices, stores, warehouses, street corners -- even in peoples' homes. But even though they're all around us, these devices are a total mystery to most people. Just what is going on inside those white tubes?

For getting a bit deeper information please read the following:

Neon light - the historical tube

Neon Light
Like fluorescent lights, neon lights produce their light through electroluminescence-a high voltage forces current through the gas which excites it and causes it to emit light. Neon tubes consist of electrodes encased in a glass tube with a phosphorescent gas. When you apply a high voltage to the electrodes,
the neon gas ionizes, and electrons flow through the gas. These electrons excite the neon atoms and cause them to emit light that we can see. Neon emits red light when energized in this way. However, unlike common florescent lights, the gases in neon lights produce visible light so there is no need for a phosphor coating. Although they are commonly referred to as "neon" lights, they may contain other gases instead, and so they are also called electric electric discharge lamps discharge lamps, or vapor lamps. A list of common colors and the gases associated with them is below:

Electric discharge lamps are constructed similar to neon lamps. The central element in a fluorescent lamp is a sealed glass tube. The tube contains a small bit of mercury and an inert gas, typically argon, kept under very low pressure. The tube also contains a phosphor powder, coated along the inside of the glass. The tube has two electrodes, one at each end, which are wired to an electrical circuit. The electrical circuit is hooked up to an alternating current (AC) supply.

When you turn the lamp on, the current flows through the electrical circuit to the electrodes. There is a considerable voltage across the electrodes, so electrons will migrate through the gas from one end of the tube to the other. This energy changes some of the mercury in the tube from a liquid to a gas. As electrons and charged atoms move through the tube, some of them will collide with the gaseous mercury atoms. These collisions excite the atoms, bumping electrons up to higher energy levels. When the electrons return to their original energy level, they release light photons.

The wavelength of a photon is determined by the particular electron arrangement in the atom. The electrons in mercury atoms are arranged in such a way that they mostly release light photons in the ultraviolet wavelength range of 254 nm. Our eyes don't register ultraviolet photons, so this sort of light needs to be converted into visible light to illuminate the lamp.

Phosphors are substances that give off light when they are exposed to light. When a photon hits a phosphor atom, one of the phosphor's electrons jumps to a higher energy level and the atom heats up. When the electron falls back to its normal level, it releases energy in the form of another photon. This photon has less energy than the original photon, because some energy was lost as heat. In a fluorescent lamp, the emitted light is in the visible spectrum -- the phosphor gives off white light we can see. Manufacturers can vary the color of the light by using different combinations of phosphors.

The classical fluorescent lamp design, which has fallen mostly by the wayside, used a special starter switch mechanism to light up the tube.

When the lamp first turns on, the path of least resistance is through the bypass circuit, and across the starter switch. In this circuit, the current passes through the electrodes on both ends of the tube. These electrodes are simple filaments, like you would find in an incandescent light bulb. When the current runs through the bypass circuit, electricity heats up the filaments. This boils off electrons from the metal surface, sending them into the gas tube, ionizing the gas.

At the same time, the electrical current sets off an interesting sequence of events in the starter switch. The conventional starter switch is a small discharge tube, containing neon or some other gas. The tube has two electrodes positioned right next to each other. When electricity is initially passed through the bypass circuit, an electrical arc (essentially, a flow of charged particles) jumps between these electrodes to make a connection. This arc lights the bulb in the same way a larger arc lights a fluorescent tube.

One of the electrodes is a bimetallic strip that bends when it is heated. The small amount of heat from the lit bulb bends the bimetallic strip so it makes contact with the other electrode. With the two electrodes touching each other, the current doesn't need to jump as an arc anymore. Consequently, there are no charged particles flowing through the gas, and the light goes out. Without the heat from the light, the bimetallic strip cools, bending away from the other electrode. This opens the circuit.

When the current flows through the bypass circuit, it establishes a magnetic field in part of the ballast. This magnetic field is maintained by the flowing current. When the starter switch is opened, the current is briefly cut off from the ballast. The magnetic field collapses, which creates a sudden jump in current -- the ballast releases its stored energy.

A fluorescent lamp's ballast works to control this. The simplest sort of ballast, generally referred to as a magnetic ballast, works something like an inductor. A basic inductor consists of a coil of wire in a circuit, which may be wound around a piece of metal.

Modern ballast designs use advanced electronics to more precisely regulate the current flowing through the electrical circuit. Since they use a higher cycle rate, you don't generally notice a flicker or humming noise coming from an electronic ballast. Different lamps require specialized ballasts designed to maintain the specific voltage and current levels needed for varying tube designs.

High-frequency electronic ballasts used in most Rohrlux hand lamps, worklights and machine lighting systems work on frequencies between 35 and 45 Khz. Due to this higher frequency the mercury cannot cool down as quickly as it does with regular magnetic ballast which work on 50 (in the US 60) Hz frequency. This leads to a quicker starting behaviour which we can recognise as a stable and constant light without flickering. An important further difference is the more efficient energy consumption. As there is less cooling down also less energy is necessary to start it up again. So finally less energy is wasted for temperature but can be used to give light.

Fluorescent lamps come in all shapes and sizes, but they all work on the same basic principle: An electric current stimulates mercury atoms, which causes them to release ultraviolet photons. These photons in turn stimulate a phosphor, which emits visible light photons.

You may, of course, know the general construction of incandescent bulbs which were invented by Thomas A. Edison: A carbon wire in an evacuated glass globe is being feeded with energy. By this the carbon wire warms up. The more heat you have the more it glows. Once you reach a glowing temperature of about 2500°C this glow wire (today mostly Wolfram wire) or carbon glows at a bright white colour. The incandescent bulbs of today mostly contain special gas mixtures to support the light output in a positive way.

Fluorescent tubes make up more than 70% of all light being produced in Germany by only using 50% of the energy required to produce this quantity of light. The lifetime of fluorescent tubes is about 8 to 12 times longer than incandescent bulbs and consume, depending on the type used, 85% less energy than conventional incandescent bulbs offering equivalent light output.

This is why fluorescent tubes are more efficient.

There are several forms of fluorescent bulbs on the marked. Besides the most common T8 and T5 tube sizes you find special energy saving bulbs as well as rounded formats and many more.

To understand light waves, it helps to start by discussing a more familiar kind of wave -- the one we see in the water. One key point to keep in mind about the water wave is that it is not made up of water: The wave is made up of energy traveling through the water. If a wave moves across a pool from left to right, this does not mean that the water on the left side of the pool is moving to the right side of the pool. The water has actually stayed about where it was. It is the wave that has moved. When you move your hand through a filled bathtub, you make a wave, because you are putting your energy into the water. The energy travels through the water in the form of the wave.

Light waves are a little more complicated, and they do not need a medium to travel through. They can travel through a vacuum. A light wave consists of energy in the form of electric and magnetic fields. The fields vibrate at right angles to the direction of movement of the wave, and at right angles to each other. Because light has both electric and magnetic fields, it is also referred to as electromagnetic radiation.

Light waves come in many sizes. The size of a wave is measured as its wavelength, which is the distance between any two corresponding points on successive waves, usually peak-to-peak or through-to-through (Figure 1). The wavelengths of the light we can see range from 400 to 700 billionths of a meter. But the full range of wavelengths included in the definition of electromagnetic radiation extends from one billionth of a meter, as in gamma rays, to centimeters and meters, as in radio waves. Light is one small part of the spectrum.

Light not only vibrates at different frequencies, it also travels at different speeds. Light waves move through a vacuum at their maximum speed, 300,000 kilometers per second or 186,000 miles per second, which makes light the fastest phenomenon in the universe. Light waves slow down when they travel inside substances, such as air, water, glass or a diamond. The way different substances affect the speed at which light travels is key to understanding the bending of light, or refraction, which we will discuss later.

Figure 2

So light waves come in a continuous variety of sizes, frequencies and energies. We refer to this continuum as the electromagnetic spectrum (Figure 2). Figure 2 is not drawn to scale, in that visible light occupies only one-thousandth of a percent of the spectrum.

The colour temperature of a light source is defined as the light colour of a normed black light source. It is measured in Kelvin (K).

KELVIN. This describes the color temperature or the description of warmth or coolness of a light source. When a piece of metal is heated, the color of light it emits will change. This color begins as red and graduates to orange, yellow, white and then to blue-white and finally to deeper shades of blue. The temperature of this metal is a physical measure in Kelvin or absolute temperature. When the sun rises it is about 1,800 Kelvin. As it rises further it continues from red to orange to yellow to white and it peaks at noon at over 5,000 Kelvin. As it set, the sun's Kelvin drops accordingly.

The colour temperature of a fluorescent bulb is being effected by using different coatings inside the glass cylinder of the bulb. The main colour temperatures used in the lighting market are:

• warmwhite = under 3300 k
• coolwhite = ca. 4000 k (Rohrlux Standard)
• daylight = over 5000 k

Colour rendering
Spectral Energy Distribution

When we look at a light source, we "perceive" a single color. In reality, we are seeing literally thousands of colors and hues of colors made up of a combination of different wavelengths of light. These different combinations, and the relative intensity of various wavelengths of light, can be used to determine a light source’s CRI.

CRI. This is the Color Rendering Index. It refers to the effect a light source has upon the colors of a given object. The sun's CRI is 100. All artificial lighting is rated to the sun.

In general, the higher the CRI rating of a lamp, the better different colors will show. However, this guideline can be misleading with certain lamp types because a high CRI sometimes makes different colors easier to distinguish, but standard colors may appear different than they actually are.

These quality differences are being expressed with the colour rendering (RA / CRI).

• 1A = RA 90-100
• 1B = RA 80-89 (Rohrlux Standard)
• 2A = RA 70-79
• 2B = RA 60-69
• 3 = 40-59

28 Watt 16mm bulb = 2900 Lumen Length 1149 mm

36 Watt 26mm bulb = 3350 Lumen Length 1200 mm

40 Watt 38mm bulb = 3000 Lumen Length 1200 mm

200 Watt E27 bulb = 3050 Lumen Length 150 mm

Advantages:

• reduced injury risk while replacing the bulbs
• strengthening the bulbs impact resistance

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