4. Try it out
Place your second piece of card stock on the ground and hold the piece with aluminum foil above it (foil facing up). Stand with the sun behind you and view the projected image on the card stock below! The farther away you hold your camera, the bigger your projected image will be.
To make your projection a bit more defined, try putting the bottom piece of card stock in a shadowed area while you hold the other piece in the sunlight.