Happy โ๏ธFebruary 1st! Have you wondered what to do with an old monthly ๐calendar? A ๐คfun kids โ๏ธscience experiment of course! This is a cool trick your kids will ๐love when they see the ๐ซmagic unfold in front of their eyes! A magically appearing image and magically disappearing ๐hydrogels ~ water-beads!

https://player.vimeo.com/video/253894355

All transparent substances have a characteristic called refractive index, which determines how much the path of light is bent/refracted when entering a material.  In optics, the refractive index or index of refraction is a dimensionless number that describes how light propagates through that medium. We see a colorless object only because its refractive index differs from the refractive index of the medium, usually the air. (Read science mystery revealed below.)

How to prepare this experiment:

Grow hydrogels: pour water over dry clear water gel beads and wait for about an hour.

Lay a laminated picture on the bottom of an empty tray (we are using an aluminum baking tray).

Wait until hydrogels are fully expanded.

Pour hydrogels over the picture and then add water and watch the magic unfold!

This tray is still filled with hydrogels which are now absolutely invisible, while the picture is visible!

Science mystery๐กrevealed: the refractive index of water is 1.333 (meaning that light travels 1.333 times slower in water than in the vacuum). The air, on the other hand, has a refractive index of almost 1. That is why we see water in the air or air bubbles in the water.

The refractive index of clear see-through hydrogels is 1.5, that is why in the water, they become completely invisible!

To observe how hydrogels grow real sped up time, see here a ๐ฅ video of how we "made" hydrogel beads in Sensory Exploration with Hydro Gel โค๏ธ๏ธ Water Beads.

For more on fun Science, see here "Rainbow ๐Colorful Skittles Fun๐ง Water Science Experiment for Kids โข๐ฌโ๏ธโ๏ธ  101 ๐ฅ Series" and see here a video-post "Lava Lamp: Oil vs ๐ ๐งWater Density Immiscibility โ๏ธExperiment with ๐ฅAlka Seltzer."