- The inner and outer surfaces of the glass flask are coated with a thin layer of silver, creating a reflective surface that helps reduce heat loss through radiation.

- This silvered surface acts like a mirror, reflecting the thermal radiation back into the flask instead of allowing it to escape.

Vacuum:

- The space between the inner and outer walls of the thermos flask is evacuated to create a vacuum.

- This vacuum significantly reduces heat transfer through conduction and convection, which are the two primary mechanisms by which heat is lost in non-vacuum containers.

- Without air or other gases, there are fewer molecules to transfer heat, resulting in better insulation and temperature retention.

Combined Effect:

- The combination of silvered glass and vacuum creates a highly efficient insulating system.

- The silver coating minimizes heat loss through radiation, while the vacuum minimizes heat loss through conduction and convection.

- As a result, thermos flasks are able to keep hot liquids hot and cold liquids cold for extended periods, making them ideal for storing and transporting beverages, soups, and other temperature-sensitive items.