Items needed:
2 paper binder clips (any size)
1 large paper binder clip
2 razor blades
1 sewing needle
1 laser pointer
Wood or cardboard base to stick pin into
Put binder clips on the razor blades so they stand up.
Jam the pin so it sticks upright out if the wood or cardboard base (I used a wooden cigar box).
Put the laser pointer into the large binder clip.
Keep moving the razor blades closer and closer to both sides of the needle.
The dual nature of photon particles vs wave theory; classical vs quantum physics!
Eventually you'll get interference lines.
