Lens

Physics is all around us, and we don't even realise.

Lenses, for example. The droplets on my shower door are acting as lenses; the camera lens was needed to take this image; and I was wearing my glasses to correct my short-sightedness.

Surface tension. The angle the surface of these water droplets is making with the glass is what determines whether they will stick to it or not. If the door was coated with teflon, the water would make an angle of 180 degrees with the surface and would roll right off.

Optical properties of materials. Why can we see through the air, the shower door, and the water droplets, but not the tiles of the wall behind?

There are countless other physics principles involved in even this simple image. It's a fascinating world.