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: Distance from gamma ray?

  1. Mar 24, 2010 #1
    Given the energy if sun were to instantly vaporize (using E = mc^2) = 2.7 x 10^47 J
    ( E = (mass of sun) * c^2)

    how far would one have to be from a gamma ray burst is order for the average power from it to be equivalent to the average power from the sun's radiation at the earth (solar constant, 1300 watt/m^2)

    I understand the problem, but I can't seem to find a formula that would solve for distance using units of the solar constant. The only thought I have is using the potential energy formula, but that is joules. Any hints on what formula to use? or solving it could also be helpful :-)

    thanks
     
  2. jcsd
  3. Mar 27, 2010 #2

    Redbelly98

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    This is weird, I don't think the problem is solvable as written.

    I guess the idea here is that the energy would be radiated evenly in all directions. So at a distance r from the sun, the energy is spread evenly over a spherical surface of radius=r.

    However, if the vaporization takes place "instantly", that implies Δt is zero hence infinite power.
     
  4. Mar 27, 2010 #3
    ahh yes sorry, I miss read the question but your technique is correct. I ended up getting the solution, the energy was 5 * 10^46 and it lasts for 120 seconds.

    I didnt get around to editing the post, sorry about that.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook