Final answer:
The illuminance of a lamp at a distance of 2m can be calculated using the formula illuminance = luminous flux / (4πr^2).
Step-by-step explanation:
The illuminance of a lamp at a distance of 2m can be calculated using the formula illuminance = luminous flux / (4πr2), where r is the distance. In this case, the luminous flux is not given, so we cannot directly calculate the illuminance. However, if the luminous flux was given, we could substitute it into the formula to find the illuminance on a book held 2m from the lamp.