Shadows are not always black!

Shadows are absolutely
fascinating to play around with.

In this Exploratorium demonstration
you can see that a black shadow is only a subset of shadows that can be
formed on the screen.

If you have multiple sources of light with different colors, then you can additively combine colors to get shadows of various shades.

In this case where you have multiple sources of light, only when the object blocks off light from all three colored light sources do you get a black shadow.

Since we do not deal with multiple colored sources of light on a daily basis, go ahead, give this simple experiment a try. It’s totally worth it!

Have a good one!

** Other FYP explorations on Shadows :

Can a single point of light always illuminate an entire room ?

On disappearing shadows of Birds and airplanes

     

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Shadows of Mount Everest & K2 at Sunrise

Mount Everest might be tiny when compared to the size of the earth and as a result we might not be able see it’s shadows on the moon.

But it would be crazy not to acknowledge the breathtaking shadows that it casts during sunrise.

* Previous post: Why don’t we see the shadow of the Everest on the moon?

Source: favrify.com

If the earth is such round, then how come we don’t see the shadow of the mount Everest on the moon ?

Just to give a perspective on how tiny Mount Everest is compared to
Earth : Mount Everest is 8850m high and the radius of the earth ~6400km.
It is only 0.1% of the radius of the earth.

But surely it does cast a shadow on the moon no doubt about it, but you just can’t see it.

Shadows cast by the moon on the other hand…

If you took a look at the recent solar eclipse animations by NASA, then you might have noticed the shadows cast by the moon during the eclipse were not circular (like yesteryears – see figure above).

But had an eerie irregular shape to it. Why is that ?

First thing to note is that if you take a circle and project it on a sphere, the shadow is no longer circles, but ellipses.* That’s why the image is elongated.

Importantly, the surface of the moon is interesting; It is irregular with lots of mountains and valleys. Hence you will not get a perfect little ellipse when you project it.

Based on whether it is a valley or a peak it would affect the shadow region during an eclipse.

As
mentioned in a previous post, eclipses on earth are too surreal to be
true because if the size of the moon were any bigger then you would be
witnessing only perfect elliptic shadows and none of this complex mess.

But if the moon’s valley were any bigger, you might never achieve complete totality.

Amazing Question. Thanks for asking!

* Unless you project it face onto the source