How Does Difference between UMBRA and PENUMBRA Work?

The umbra and penumbra are parts of a shadow that happen when something blocks light, like when you’re playing with shadows on the floor.

Imagine you're holding a flashlight, shining it onto the wall. Now put your hand between the flashlight and the wall. You’ll see a dark shape, that’s your hand's umbra, the totally blocked part of the shadow. But if you look closely, around that dark shape, there’s a lighter gray area, that’s the penumbra, where only some of the light is blocked.

Now imagine instead of your hand, it’s the Moon blocking the Sun during an eclipse. The umbra is the place on Earth where the Sun is completely blocked out, you get total darkness, like nighttime! The penumbra is around that spot, and there, only part of the Sun is blocked, so it's still a little bright, like late afternoon.

It’s just like when you're outside on a sunny day, and you walk between two trees. One tree blocks all the light, that's your umbra, but if you move a bit, some light still shines through, that's your penumbra!