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: Light Intensity question

  1. Apr 29, 2008 #1
    [SOLVED] Light Intensity question

    The light (electromagnetic) output of a bulb is 40 W. How much energy passes through a 40 cm^2 area element aligned perp. to the light rays?

    I know that I = Power/Area, but I thought that Power = W(aka. energy) /t , and the problem has no reference to time.

    What am I missing?
  2. jcsd
  3. May 1, 2008 #2
    Without time this question is meaningless.
  4. May 1, 2008 #3
    Yea we told our teacher, so now the t= 4 seconds, and obviously now the problem is super easy. W=Pt

    W= 40 W (4 s)

    W=160 J
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook