41.The following processes take place during the launching of a rocket : 1. Rocket fuel is burnt. 2. Gases are produced. 3. Rocket moves in the forward direction. 4. Gases come out with momentum in backward direction. The correct sequential order in which the above processes occur, is

42.The principle of working of periscope is based on

43.The heat required to vaporise the refrigerant in the cooling unit of an electric refrigerator is furnished by

44.The lightning conductor used in building, protects the building by

45.Which of the following substances exhibit the property of sublimation ?