A manufacturer tests three insulating panels for the doors of identical freezers. The panels are tested with equal exposed areas under identical inside and outside temperature conditions.
| panel | thickness in mm\mathrm{mm}mm | thermal conductivity in W m−1 K−1\mathrm{W\,m^{-1}\,K^{-1}}Wm−1K−1 |
|---|---|---|
| P | 20 | 0.022 |
| Q | 40 | 0.035 |
| R | 50 | 0.020 |
The cooling systems are switched off.
Explain which panel would make the temperature inside its freezer rise most slowly.