reflecction of light when it hits particles in the air?
may also be the diffraction of light? (ie when it passes between e small amt of space between particles?)
from what I've read .. I am supposed to learn that the silver lining which we see is due to e diffraction of light. but i don't understand how diffraction of light results in e particularly bright parts along e edge of the clouds. shouldn't e light waves spread out? such that it would also cover...