Final answer:
Spaces where only minimal detail is needed may require at least 108 lux, equivalent to 10 foot-candles of lighting. Illuminance for tasks like desktop work is higher at 500 lux, where adjustments to light fixture height are critical to meet these requirements. Lighting efficacy and the inverse square law of illuminance are key concepts in understanding how light levels should be managed in different environments.
Step-by-step explanation:
Areas that require 10 foot-candles of lighting, which is approximately 108 lux, include spaces where minimal detail is necessary. According to the Occupational Safety and Health Administration (OSHA), more detailed tasks, such as desktop work, require higher levels of lighting, around 500 lux. For example, an office space may have lighting fixtures that need to be adjusted to provide the right level of illuminance. If the existing lighting at a height of 2.50 meters only provides 300 lux, the fixtures should be lowered to 1.22 meters to achieve the recommended 500 lux. This adjustment can be calculated based on the inverse square law of illuminance, which explains how illuminance decreases with the square of the distance from the light source.
To illustrate how greatly light fades with distance from its source, at a distance of 3 meters, the illuminance drops to around 17.7 lux, which is significantly lower than what is required for tasks like reading. This is why proper lighting is crucial in areas where visual tasks are performed to avoid eye strain. It's also worth noting the concept of luminous efficacy, which recognizes the efficiency of light sources in terms of lumens per Watt. This is a more accurate representation of brightness than Watts, which was traditionally used to describe the power consumption of incandescent bulbs.