How to make a cup with photos when you first arrive at the water?

According to the amount of water, the lens shape caused by the special structure of the cup is changing. Enlarge the image at the level of the cup and the human eye can see it!

Because you put your favorite photo at the bottom of the cup ... some cups have protruding lenses at the bottom ... your photo is enlarged ... you can see it ... this is the refraction principle of physical light.

There is also a kind of cup that can't hold water, also called greedy cup.

Using the pressure difference of the water column, the water rises and then flows to a lower place, which is the principle of rainbow absorption phenomenon.