By which method are the walls of a thermos flask galvanized to minimize heat transfer?

The correct answer is [C] Radiation. The walls of a thermos flask are designed to minimize heat transfer by radiation through galvanization, which involves coating the inner surfaces with a reflective material, often aluminum or a similar substance. This shiny coating reflects infrared radiation back into the liquid, thereby reducing heat loss through radiative transfer. While the vacuum between the flask’s double walls effectively eliminates heat transfer by conduction and convection, it is the reflective inner surface that specifically targets radiation. This reflective layer ensures that the heat is kept within the flask when the contents are hot, or that external heat is reflected away when the contents are cold. This comprehensive approach is what makes a thermos flask so effective at maintaining the temperature of its contents for long periods. Thus, galvanization primarily addresses heat transfer by radiation, making it a critical component of the thermos flask’s design.