English: We can observe many physical phenomena in a glass of half-brewed tea. Both the water and the glass refracts light, and this makes the image of the tea bag strangely distorted. We can see several partial reflections both in the water and on the glass, however, on the back side of the glass we can see the image of the bag with total reflection, in triplicate. On the table, in the shadow of the glass, we can see refraction caustics, which is partially colored because of the dye of the fruits, which is dissolved in the water, absorbs light of different colours differently. The solution (i.e. the fruit tea) is denser than the water, so a convection develops, and we can see the streamlines in which the tea flows downwards, with a closely stationary flow. We can also see some bubbles on the bag, which stick to the bag because of surface tension.

English: A glass of physics