The green flash
A) is best seen through cirrostratus clouds.
B) requires the presence of ice crystals.
C) occurs because green light is scattered more readily than blue light.
D) involves both refraction and dispersion.
E) is most readily observed when the observer is in a mountain valley.
Question 2
Halos
A) are most common when the sky is clear.
B) require a thin and uniform layer of ice crystals.
C) are usually found within five degrees of the Sun.
D) occur with the Sun, but not the Moon.
E) are caused by reflection of light.