Light from a physicist’s perspective

What we call light is a form of energy that beams from a light source, for example the sun or a light bulb. To a physicist, light is electromagnetic waves where each wave varies in length.

In everyday speak, visible light is the radiation that falls in the wavelength range of 380-780 nanometre. Radiation with shorter wavelengths is called ultraviolet (UV light) and is invisible to the eye, but can still give us a sunburn. Radiation with longer wavelengths is called infrared (IR). This type of lighting too is invisible to the eye but can be perceived as heat. The various wavelengths of visible light represent different colors. These are the colors we see in a rainbow, or when light is split by a prism.

The surface structure of an object causes some wavelengths to be reflected, while others are absorbed. The reflected wavelengths, when combined, create the perceived color we get from the object.

It’s the brain that ”sees”

It’s only when light affects the nerve cells in the retina of the eye that our view of the world around us is created – inside the brain. For this to happen light must be collected on the retina via the eye lens.

A muscle performs the work required to change the cupping of the lens to achieve correct focus. This ability is gradually reduced with age. People over the age of 40 compensate for this using reading glasses and better lighting.

In an infant, the lens is entirely transparent, but with age it muddles. For this reason too an aging eye needs better lighting than a younger one. The muddling also causes light to spread inside the eye, and light sensitivity increases.

The pupil is the opening through which the eye lets light in, with the pupil widening in low light and becoming more narrow in strong light. The pupil also narrows at short viewing distances. In other words, more light is required when working close to the eye.

The retina of the eye is made up of drops and rods. The drops affect the ability to see colors and are positioned more closely together inside the yellow area. The rods are very sensitive to light and are useful in low light conditions. The rods also register the grey tones of light between black and white.

An older person is more affected by blinding light than a younger person. An older eye also has a reduced capability of adapting to the current lighting conditions. When working in the dark it is therefore important to be able to adjust the light source of instruments and other equipment.

Good lighting – a profitable investment

Often, technical arguments are the sole resource when making decisions on workplace lighting, at the cost of ergonomic considerations. Research shows that good ergonomic lighting in most cases will prove to be profitable. One important aspect to achieving good productivity results is to consider lighting at an early stage in a project. Good lighting can usually be achieved with simple solutions.

Precision work and work with moveable objects requires a lot of light in the right place, but too much light or light pointed in the wrong direction will cause blinding and contrasting issues. Blinding light always leads to poor productivity. There are three types of blinding: direct blinding, reflective blinding and contrast blinding.

• Direct blinding
  The light should never hit the eye directly. If the source of the light can be seen, direct blinding will occur.
• Reflective blinding
  Reflective blinding occurs when the light from a lamp is reflected in a surface within view.
• Contrast blinding
  This type of blinding occurs when there are strong contrasts within the field of view. A good rule of thumb is that luminance in the inner field of view, where the object is located, should be three times higher than the surroundings, which in turn should be three times brighter than the peripheral. Transitions between surfaces with a luminance ratio of 1:5 reduces the ability to see at the same rate as when the intensity of the light is reduced from 1000 to 30 lux. The eye’s ability to adapt is affected, and it grows tired unnecessarily fast.

Correct color representation

The composition of the light is important to achieve correct color representation. Daylight provides a color representation that we perceive as natural. Color representation for LED lights with LED chips of high quality is nowadays considered first class, comparable to classic halogen light bulbs.

Individual adaptation

The intensity of light must always be adapted to the type of work being performed. Two different workplaces can’t be expected to have the same requirements for their respective lighting solutions. The fitting of lathe steel, for example, requires a light intensity of 3000 lux while regular office work only requires 1000 lux. A 60W light bulb at a distance of 40 cm will provide 600 lux.

Lighting of a workplace area or object must always mesh with the general lighting of a room or facility. On the other hand, general lighting can never replace task-specific and individualized lighting.

A well-planned workplace lighting solution reduces the need for strong and dominating general lighting, which can consequently be dampened. The room thus becomes nicer to spend time in, and a lower overall effect is required.

Positive effects

Correctly executed workplace lighting provides positive effects to staff, performance, error frequency and energy consumption – all important factors on their own in any operation. To plan so that basic needs for workplace lighting are met can, in other words, be highly profitable in more ways than one.