Air conditioner and glasses: what they have in common

1. Step 1. Air conditioner — is made of — Refrigerant. Inside is a refrigerant.
2. Step 2. Refrigerant — is made of — Ammonia. Ammonia was one of the first refrigerants.
3. Step 3. Ammonia — is material for — Maser. The first maser ran on ammonia.
4. Step 4. Maser — evolved into — Laser. A laser is an optical maser.
5. Step 5. Laser — is used in — Laser surgery. A laser.
6. Step 6. Laser surgery — works like — Glasses. Laser vision correction solves the same problem as glasses — it changes refraction, but in the cornea itself.

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