Final answer:
The student's question about calculating illuminance can be solved using the formula Illuminance = P / (4πr²). For a bulb with a luminous flux of 2,000 lm positioned 2 meters away from a book, the illuminance is approximately 39.79 lux.
Step-by-step explanation:
The student's question relates to the formula for calculating illuminance, which is a measure of how much luminous flux (measured in lumens) falls on a certain area. The formula for illuminance is given by Illuminance = P / (4πr²), where 'P' is the luminous flux in lumens (lm) and 'r' is the radius in meters (m) from the light source to the surface on which illuminance is measured. To solve the given problem, we have a luminous flux (P) of 2,000 lm, and a distance (r) of 2.00 m. Using the formula, we calculate the illuminance on the book as:
Illuminance = 2000 lm / (4π(2.00 m)²) = 2000 lm / (4π(4 m²)) = 2000 lm / (50.265 m²) = 39.79 lx
Therefore, the illuminance on the book held 2 meters away from a 2,000 lm bulb is approximately 39.79 lux (lx).