Thickness of ice on a lake is 5 cm and the temperature of air is `-20^(@)C` . If the rate of cooling of water inside the lake be 20000 cal `min^(-1)` through each square metre surface , find K for ice .

Explanation

To find the thermal conductivity \( K \) for ice, we can follow these steps:

### Step 1: Understand the Given Information
- Thickness of ice, \( L = 5 \) cm = \( 0.05 \) m
- Temperature of air, \( T_B = -20^\circ C \)
- Temperature of the surface of ice, \( T_A = 0^\circ C \) (since it is in contact with water)
- Rate of cooling of water, \( Q = 20000 \) cal/min/m²

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