1. Not finding help here? Sign up for a free 30min 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!

A few light problems?

  1. Mar 18, 2005 #1
    1) Find the illumination 4.2 m below a 415 lm lamp.

    2) A screen is placed between two lamps so that they illuminate the screen equally. The first lamp emits a luminous flux of 1445 lm and is 2.7 m from the screen. What is the distance of the second lamp from the screen if the luminous flux is 2350 lm?

    3) Two lamps illuminate a screen equally. The first lamp has an intensity of 101 cd and is 4 m from the screen. The second lamp is 5 m from the screen. What is the intensity of the second lamp?


    These should be very easy. However, I'm doing this for a friend and I don't have his book or any of the formulas. Help me out?
  2. jcsd
  3. Mar 18, 2005 #2
    Intensity is proportional to the inverse square of radius.

    I = L / R^2, this should help you solve all three of hte above questions, since they are basically the same.
  4. Mar 19, 2005 #3
    I = L / R^2
    i = 415/4.2^2
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: A few light problems?
  1. A few problems (Replies: 3)

  2. Few problems (Replies: 1)

  3. Few Problems (Replies: 22)

  4. A few problems (Replies: 4)