Optical Phenomena: DGCA Aviation Meteorology questions

Light passing through water droplets, ice crystals, fine dust or layers of air at different temperatures paints rings, glows and false images across the sky. Haloes and coronae also tell you whether a cloud is made of ice crystals or water droplets.

All 20 questions are short recall items on aurorae, coronae, haloes, Bishop's ring and mirages. DGCA papers have used 4 of these questions.

A halo comes from refraction through ice crystals and shows red on its inner edge. A corona comes from diffraction by water droplets, sits close to the sun or moon and has red on the outside. A superior mirage needs a strong inversion, an inferior one a surface far hotter than the air above.