How to change the drawing arrow on paper?

To do this experiment, you need to prepare 1 bottle of water, 1 cup of water, 1 color paper and 1 black ink brush. First, we draw 3 arrows on a colored paper and fill them with brush. Then, place the paper against the wall and leave the glass of water in front of the paper. Slowly pour water into the glass, you will see 3 arrows gradually reversing when the water rises.

The explanation for this experiment is due to light refraction, in which a glass of water acts as a lens.

In the above experiment, when the water is not poured, in the glass is air (the refractive index is 1 much smaller than the refractive index of glass 1.5), so that only a glass of light and light rays will occur. only partially bent so that through the glass, the arrows are not straight.

The arrows drawn in black ink automatically change direction when you look at them through a glass of water.

When pouring water into the glass, the refractive index of the water is about 4/3 approximately equal to the refractive index of glass 1.5 with the circular structure of the glass of water (equivalent to two convex curved faces facing each other). At this time, the glass of water is like a focusing lens so the image passes through the lens system (lens of glass of water and eye lens), making us see the reverse image of the arrows.