Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The size of the sun using pinhole imagery

  1. Aug 28, 2005 #1
    Does intensity of the sun affect this? I keep trying to do it, and when you have a square shape you should still see an image of the sun.. right? Well it is not working! I live in a place with VERY intense sun and no clouds... could this be the problem?

    Any help!? Thanks so much...
  2. jcsd
  3. Aug 28, 2005 #2


    User Avatar
    Science Advisor
    Homework Helper

    What, exactly, are you seeing? How big is the hole? How far apart are the hole and your imaging plane?
  4. Aug 28, 2005 #3
    OK... what I did was cut a square in the center of a piece of stiff construction paper. Then I covered the square with a piece of tin foil. Then I punctured the middle of the piece of tin foil with a sewing needle (very small). When I went outside I started out with the pinhole about a foot away from the piece of white paper on the ground that I was trying to project the image onto. I got a tiny dot... slightly bigger than the pinhole itself... very difficult to measure. So I moved the pinhole further away and closer to try and make the image bigger with very little change. So I have put it very close and about four and a half feet away. We are also meant to try it with a small square and it is still meant to show an image of the sun, but when I make a small square that is exactly what is projected on the piece of white paper!

  5. Aug 28, 2005 #4


    User Avatar
    Science Advisor
    Homework Helper


    As a rough guide, basic geometry gives the spot size as

    [tex]y = D_H + L \theta[/tex]

    where [itex]D_H[/itex] is the diameter of the hole, [itex]L[/itex] is the distance between the hole and the image plane and [itex]\theta[/itex] is the angular diameter of the Sun (in radians). In order to get a "good" image of the Sun, you will need to arrange for [itex]L \theta[/itex] to be larger than [itex]D_H[/itex].

    Good luck!
  6. Aug 30, 2005 #5
    experimentally speaking, you may put some smoked glass otside the pinhole to check if light intensity affects the spot size. that is one of the way to do physics.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook