Pinhole and electrical telegraph: what they have in common

1. Step 1. Pinhole — is part of — Camera obscura. It projects an inverted image.
2. Step 2. Camera obscura — evolved into — Camera. A camera is a camera obscura with a light-sensitive layer.
3. Step 3. Camera — is part of — Bubble chamber. Photographing the tracks.
4. Step 4. Bubble chamber — has part — Electromagnet. The field bends the tracks.
5. Step 5. Electromagnet — is part of — Electrical telegraph. Morse’s receiver.

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