Refractometry
Refractometry is a way to measure how much sugar or other stuff is dissolved in a liquid by shining light through it.
A beam of light bends when it passes from air into a liquid. The more sugar in the liquid, the more the light bends. A glass jar holds two layers: plain water on the left, sugar syrup on the right. A straight straw placed across both layers looks bent at the boundary, and more sugar makes a bigger bend.
Explaining refractometry by grade level
Light bends when it goes through juice. More sugar makes light bend more. A special tool measures that bending. That tells you how sweet the juice is.
Projects that explore refractometry
When light passes through a liquid, dissolved sugar bends it — and a refractometer reads exactly how much. In this experiment, an automatic refractometer measures total dissolved sugar in each juice sample, complementing the HPLC data that separates out individual sugars. Together, the two instruments tell a fuller story: the refractometer reading reveals whether a "premium" apple juice actually contains more dissolved sugar than a reconstituted concentrate.
Place three drops of freshly juiced apple on a refractometer and it measures dissolved sugar in degrees Brix — a standard unit for sugar concentration. As apples sit on the counter after leaving cold storage, their sugar levels shift. By recording Brix readings for each variety twice a week over several weeks, you build a sugar curve for granny smith, golden delicious, and red delicious apples. That means you can compare not just how sweet each variety is, but how fast it changes once it comes out of the refrigerator.