This java applet let you play with a virtual pinhole viewer.
How could the light from the source get through the tiny pinhole to create a complete image of the source?
Why is the image upside down on the screen?
Think about the path of light.
What do you think would happen if you enlarge the pinhole size?
Does the image become more or less clear?

screen distance=(valid value: 150 to 430, integer value only)

How to play:
Click LEFT mouse button

  1. at blue dots at character Fto show the light path emitted.

  2. at bottom near character F,and drag left/right to move F along the z-axis.

  3. at pinehole and drag the mouse to change the location of the pinehole box.