question_answer 36)

  'Ozonehole' means (a) a large sized hole in the ozone layer                 (b) thinning of the ozone layer (c) small holes scattered in the ozone layer          (d) thickening of ozone in the ozone layer

Answer:

  (b) The part of atmosphere which is rich in ozone may be called ozone layer, ozonosphere, ozone umbrella or ozone shield. In 1985, Farman found that ozone layer had thinned out over Antarctica. It was called on ozone hole. A similar but smaller hole was also found over arctic region by Augestein (1987). It has grown in size from 13 million in 2000. Atmospheric ozone is measured by spectrometer and is expressed in Dobson Units (DU).