(Requires a calculator that can compute square roots.)

Chapter 7, Problem 14

(choose chapter or problem)

(Requires a calculator that can compute square roots.) Film studios, photographers, and the lighting industry usually measure light intensity in foot-candleshistorically, the amount of light one candle generates on a surface one foot away. Light intensity I (in foot-candles) is directly proportional to candlepower P (which measures how much light is generated by a light source) and inversely proportional to the square of the distance, d, from the light source. (See Section 7.5, Example 8, p. 426.) The relationship is the inverse square law I P/d2 where I is measured in foot-candles, P in candlepower, and d in feet. a. A students angle-arm lamp can be positioned as close as 1 foot above the work surface and as far as 3 feet, measuring to the center of the bulb. If the 60-watt bulb has 70 candlepower, how many foot-candles illuminate the surface at the lowest and the highest positions? b. Where would you position the bulb to get 50 foot-candles of illumination, the standard level recommended for reading?