Which one of the following is measured in Dobson units $(DU)$?

The ozone layer in the upper atmosphere $(stratosphere)$ is destroyed by which of the following chemicals, or which chemical is responsible for the reduction of the ozone content of the atmosphere?

Define the following terms:
$(i)$ Snow blindness
$(ii)$ Ozone hole

World Ozone Day is celebrated on

In which year was the Montreal Protocol,which aims to protect the ozone layer,signed?

The full form of $CFCs$ is . . . . . . .