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!

Photons per square CM

  1. May 9, 2010 #1
    I was just looking at a light source from a few miles away obscured by several trees and thought "wow, that's pretty bright for such a small light (an airplane's flash) to register from such a distance".

    So, a small flash travels, say two miles, hits a small opening, say two or three inches, and travels about another quarter mile to my eye and STILL registers pretty bright. It must take quite a large amount of photons to pass between the gap in the leaves of a tree and still make a bright "impact" on my iris.

    What kinds of photon density tests have been done and if so, how many would it take to register a reaction in our vision?

  2. jcsd
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Can you offer guidance or do you also need help?
Draft saved Draft deleted

Similar Threads - Photons square Date
B Why the speed of light squared? Wednesday at 7:45 AM
I Image formed by photons Tuesday at 1:05 PM
I Photon upconversion and second law of thermodynamics Feb 18, 2018
B Composition of Light Feb 14, 2018
B Parallel photons Feb 4, 2018