why are rain clouds black?

Clouds are formed of tiny water droplets and ice crystals that float in the air.Generally,clouds appear white in colour because of the scattering of sunlight.As you know,sunlight consists of seven colours of a rainbow.When light passes through clouds,all the seven clouds are scattered by the water droplets and ice particles and together they produce a white appearance.
   Rain clouds,however,are densely packed with water droplets,ice and snow particles.So,light cannot penetrate them.Thus we do not see the rays from the sun and this results in a dark effect.
    If we look from an aircraft flying at high altitude,these dark clouds will look white.This is due to the reflection of light falling on them.That means the same clouds appear both dark and white at the same time!
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