telescope
camera
microscope
periscope
Oxygen
Nitrogen
Carbon dioxide
Helium
Prevents harmful infra-red rays of the sun from reaching the earth
Prevents radiation escaping the earth, hence keeping it warm
It is essential for rainfall
It filters harmful ultra -violet rays of the sun
mass
temperature
electric current
air
Chandragupta
Ashoka
Kunal
Harshavardhan