Concept about Lighting – This book covers the entire syllabus of “Community Health Nursing” prescribed by the Universities of Bangladesh- for Basic and diploma nursing students. We tried to accommodate latest information and topics.
This book is examination friendly setup according to the teachers’ lectures and examination’s questions. At the end of the book previous university questions are given. We hope in touch with the book students’ knowledge will be upgraded and flourished. The unique way of presentation may make your reading of the book a pleasurable experience.
Concept about Lighting
Definition
Light is the electromagnetic radiation to which the human eye is sensitive.
Criteria or requirements of good lighting:
Good lighting is essential for proper vision. For efficient vision, the following light factors are essential:
1. Sufficiency
- Should be sufficient (not excess or poor) to carry on the intended work, without any eye strain.
- Minimum illumination for satisfactory vision; 15 to 20 foot candles.
2. Uniform distribution
- Should be uniform, and having the same intensity, over the whole field of work.
- Should be properly dispersed without production of shadows, which are necessary for efficient vision
3. Absence of glare
- Glagre means excessive brightness; it hurts the eye and decreases critical vision. It is an important cause of accidents, especially road accidents.
- Glare may be “direct” from a light source or “reflected” from surfaces such as table tops and polished furniture.
4. Absence of sharp and contrasting shadows
Shadows should not be present in the field of vision, because they interfere with vision.
5. Steadiness
- The source of light should be constant.
- It should not flicker,
6. Colour of light
- Should be suitable for eye.
- Should as far as possible be approximate to the day light colour.
7. Surroundings
- High levels of illumination will be required where there is little colour contrast.
- Contrasting colours are useful to prevent accidents, e.g. culverts, bridges etc.
Effects of ill (bad) lighting
- Eye strain
- Headache
- Irritability of temper
- Postural deformities such as wry neck, round shoulders etc.
- Great liability to accidents
- Dislike for work and early exhaustion
- Loss of efficiency, lack of concentration
- In factories –
Chance of more accidents
Quantity and quality of the products may fall.
- Among the mine workes – Nystagmus (Miners nystagmus).
Effects of light on health (Biologic effects of light)
- Breakdown of bilirubin
- Stimulation of physical activity
- Stimulation of melanin synthesis.
- Activation of vitamin D precursor in the skin, thus help in synthesis of vitamin D.
- Secretion of adrenocortical hormone.
- Stimulation of food consumption
Sources of light
1. Natural lighting: Day light (Sunlight)
Factors to utilize day light efficiently –
- Architectural pattern of the building.
- Time of the day
- Season
- Weather and atmospheric pollution.
2. Artificial lighting:
a. Electrical lighting –
- Filament lamps
- Fluorescent lamps
- Energy saving bulbs
b. Oil lamps, candles, torches.
c. Lighting by gas
Systems of artificial lighting
There are five systems of artificial lighting:
1. Direct lighting – 99 to 100 percent of the light is projected towards the working area.It is efficient, economical, but tends to cast sharp shadows.
2. Semi-direct lighting – 10 to 40% of the light is projected ceiling, so that it is reflected back
on to the object.
3. Indirect lighting – 90 to 100 per cent of the light is projected towards ceiling and walls. It gives a general illumination of the whole area.
4. Semi-indirect – 60 to 90% of the light is directed upwards and the rest downwards.
5. Direct-indirect Here light is distributed equally.
Lighting standards
1. The eye responds to a range of illumination ranging from 0.1 lux (full moonlight night) to 100,000 lux (bright sunshine).
2. Recommended illumination for practical situations and various activities are:
a. Casual reading = 100 lux
b. General office work= 400 lux
c. Fine assembly= 900 lux
d. Very severe tasks 1300-2000 lux
e. Exceptionally difficult task like watch making, jewellary etc. 2000-3000 lux.
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