Question

what is the role of silver coating inside a thermos bottle

Answer 1

The thermos flask has one main purpose, that is to maintain the temperature on the liquid put in it, whether cold or hot. The thermos flask has been designed  to use efficient methods to prevent heat loss or gain. These are some of the way this is made possible:
1. Prevention of heat transfer by RADIATION:This is made possible by the silver coating on the inner bottle which reflects heat thus preventing heat transfer. 
2. A vacuum between its two walls:This vacuum prevents heat loss or gain through convention
3. Thin glass walls:The glass walls have been designed to be extremely thin to prevent heat loss by conduction. 
Therefore, 
The silver coating is meant to ensure that heat transfer through the process of radiation is prevented. 
TYSM@kundan.............