In this activity, students use colour-changing, ultraviolet-sensitive beads to observe how sunscreen can block the harmful effects of the sun's rays.
One type of light radiating from the sun, called ultraviolet (UV) light, is visible to insects and birds, but not to humans. UV radiation helps us make vitamin D in our skin, but too much of it can cause radiation burns (sunburns) and skin cancer.
Unlike plants, humans don't needs photosynthesis to make our food and survive, but the sun is still very important for us. Among other things, humans need the sun to help our skin make vitamin D. Without vitamin D our bones cannot grow properly and they get soft and bend, causing the bone malformation called Rickets.
How can you tell if you have had enough UV radiation? Your skin will change colour when it is exposed to enough (or too much) UV radiation. Unfortunately, it can take a few hours for a tan, or burn, to show.
UV beads have special chemicals that change colour very quickly when UV light hits them. Sunscreen blocks some UV light so the beads change colour more slowly if they are covered with sunscreen.