Photovoltaic effect and chisel: what they have in common

1. Step 1. Photovoltaic effect — is used in — Photoresistor. Photoconductivity.
2. Step 2. Photoresistor — is part of — Street light. Switching on at dusk.
3. Step 3. Street light — is part of — Tunnel. Lighting.
4. Step 4. Tunnel — uses — Chisel. Hezekiah’s Tunnel was cut by hand with chisels.

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