UV Absorption
UV Absorption is what happens when a material soaks up ultraviolet light instead of letting it pass through.
Hold a piece of dark sunglasses glass between a flashlight and the wall. The shadow is darker because the lens absorbed some of the light. Sunscreen works the same way for UV rays you cannot see — it soaks up the invisible light before it can reach your skin.
Explaining uv absorption by grade level
Think about putting sunscreen on your skin before going outside. The sun sends invisible rays you cannot see. Sunscreen works like a shield. It soaks up those invisible rays so they never reach your skin. Thicker sunscreen soaks up more of the rays. That is how sunscreen keeps you from getting a sunburn.
Projects that explore uv absorption
Different materials soak up ultraviolet light at different strengths, and the extinction coefficient measures how strongly a substance absorbs light at a specific wavelength. You dissolve a small amount of sunscreen in ethanol, dilute it into six samples at different concentrations, then measure how much UV light each sample absorbs near 310 nanometers using a UV-visible spectrophotometer. Plotting absorbance against concentration gives a Beer's Law graph, and the slope of that line is the extinction coefficient — a steeper slope means the sunscreen absorbs more UV light per gram. Comparing extinction coefficients across several SPF ratings reveals whether higher SPF products actually show stronger UV absorption.
A UV-absorbing material soaks up ultraviolet light instead of letting it pass through. You coat five glass sheets with soap mixtures, each containing a different concentration of octyl salicylate — a common UV filter in sunscreen — ranging from 0 to 8 percent. Each sheet sits over a box with a UV meter inside, placed in direct sunlight. Comparing the UV index reading with and without the coated glass shows that higher concentrations result in greater blockage of UV radiation.