1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Calculus optimization problem?

  1. Jan 10, 2013 #1
    The illumination from a bulb varies directly as the intensity of the light and Intensity varies inversely as the square of the distance from the source. Two bulbs are placed 54 feet apart. The intensity, Ia, of bulb A is 64cd, and the intensity, Ib, of bulb B is 125cd. At how many feet from bulb A along the line between the two bulbs is the total illumination the least?

    I have no idea how to start this problem...I thought about using optimization but I'm not sure where to start
  2. jcsd
  3. Jan 11, 2013 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    If you were dealing with a single bulb, what would the illumination of say bulb A be at a distance x from the bulb?

    Similarly, what would the illumination of bulb B be at a distance x?

    Assuming that the illumination at a point between the two bulbs A and B is additive, how would you go about finding the point of least illumination?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook