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11-115.

Multiple Choice: The luminous intensity of a light bulb, measured in lumens/ft2, varies inversely as the square of the distance from the bulb. E = 5.2 lumens/ft2 when for a watt bulb. If you are moving away from a watt bulb at a speed of ft/sec and you are feet from the bulb, the luminous intensity is changing at the rate of: Homework Help ✎

  1.  lumens/ft2

  1.  lumens/ft2

  1.  lumens/ft2

  1.  lumens/ft2

  1.  lumens/ft2

When ?

Substitute in the known values and solve for E′.