Military drone and incandescent light bulb: what they have in common

1. Step 1. Military drone — has part — Smartphone camera. Reconnaissance cameras.
2. Step 2. Smartphone camera — has part — Lens. A lens of several elements focuses the image.
3. Step 3. Lens — is part of — Film projector. A projection lens.
4. Step 4. Film projector — has part — Incandescent light bulb. The light source (formerly an arc).

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