A window with double-pane is used for insulating a room thermally from outside. It consists of two glass sheets, each of area A and thickness d with a separation x between them. At equilibrium, the room-glass interface and glass-outside interface are at constant temperature of `T_r` and `T_a` respectively. What will the rate of heat flow through the window pane? The thermal conductivity of glass and air are `K_1` and `K_2` , respectively.

Explanation

To find the rate of heat flow through a double-pane window consisting of two glass sheets with a separation filled with air, we will follow these steps:

### Step 1: Identify the parameters
- Let the area of each glass sheet be \( A \).
- The thickness of each glass sheet is \( d \).
- The separation between the two glass sheets is \( x \).
- The temperature at the room-glass interface is \( T_r \).
- The temperature at the glass-outside interface is \( T_a \).
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