Light is an e.m wave..but what is brightness(coming from clouds in rainy days)

Question

Light is an e.m wave..but what is brightness(coming from clouds in rainy days)

Answer 1

It's scattered light.

in clear sky , shadows are sharp as rays come straight direct from the sun. In cloudy sky rays get scattered in different directions, giving a glow to clouds. shadows get dim and blurred. that's what changes the effect

Answer 2

lightning...

Answer 3

The sun's UV rays still penetrate and that is why sunscreen is still important on cloudy days.  The sun is magnificent in both magnitude and size, it's amazing that earth is the perfect distance for sustaining life.  God made it truly amazing, big bang couldn't have chanced anything.

Answer 4

It is refracted sunlight. It is light and therefore part of the electromagnetic spectrum. Also, UV is not visible.