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: Photons/Second from a 100W bulb.

  1. Jun 16, 2011 #1
    1. The problem statement, all variables and given/known data

    Estimate how many photons of visible light (500 nm) are emitted by a 100 W Bulb.

    The answer on the sheet says approximately 10[itex]^{20}[/itex] photons/second

    However when I work it out I get a slightly different answer.

    2. Relevant equations

    I used that 1J=1W/s or E=P/t

    Also Energy of one photon is E=hf so if you had lots of photons you would [itex]\Delta[/itex]E=nhf where n is the number of photons.

    3. The attempt at a solution

    I get 2.5[itex]\times[/itex]10[itex]^{20}[/itex] photons/second
  2. jcsd
  3. Jun 16, 2011 #2


    User Avatar
    Homework Helper
    Gold Member

    You solved the problem correctly.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook