Write a note on a double-walled flask or a thermos.

(N/A) double-walled flask or thermos bottle is an arrangement designed to minimize heat exchange between the surroundings and the system inside it. It consists of a cylindrical glass vessel with two walls.
$1$. $A$ silver coating is applied to both the inner and outer surfaces of these walls.
$2$. The inner silvered wall reflects thermal radiation back into the system,preventing heat loss.
$3$. The outer silvered wall reflects incoming thermal radiation from the surroundings,preventing heat gain.
$4$. The space between the two walls is evacuated (vacuum),which effectively eliminates heat transfer via conduction and convection.
$5$. The flask is sealed with an airtight insulating cork to prevent heat loss through evaporation or air circulation.
$6$. Consequently,the substance inside remains at its initial temperature (hot or cold) for an extended period.