Why can you see through water? (From a real 4 y.o.)
In: Physics
All things in the world are made up of tiny building blocks called atoms, and molecules (which are like blocks of atoms arranged in particular shapes, like how you have lego bricks that are 2×4 or 3×1 or a 2×1 slant, and so on).
Whether you can see through something depends in what molecules the thing is made from, what shapes and how far apart they are.
Different colours of light have different sizes (different wavelengths), and if the object the light hits has exactly the right molecules and shapes, the bits of light that hit it can fit exactly into the spaces around the molecules and they get absorbed/trapped by the molecules in the object, and so the bits of light don’t pass through it.
But if the spaces around the molecules is not exactly the right shape for the colour of light, the light can bounce through the object and come out the other side where it can go into your eye and you can see it.
For something like water, the reason you can see through it is because the molecules are the wrong shape to absorb light in what we call the “visible spectrum”, which is all the colours of the rainbow from red to indigo/violet. Any light of any of those colours will bounce through the water and come out the other side where you can see it.
But with water in particular, the molecules are the right shape to absorb a different type of light – water is very good at absorbing microwave light, which is a type of light that you can’t see with your eye. That’s why food gets hot in the microwave oven – it spits out a bunch of microwave light, and all the water in the food traps those bits of microwave light, which makes the water heat up and makes your food hot.
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