UV Light and Sunscreens

Introduction

Sunscreens are available in many different types and with many different levels of protection. The most common measure of protection from UVB light is the SPF factor. SPF, or sun protection factor, describes the increased amount of time you can be in the sun before your skin starts to burn. For example, a sunscreen labeled SPF 8 means that you can be out in the sun eight times longer before burning than you would without using any protection. Products range from SPF 0 to SPF 50 or higher. But is SPF 50 really twice as protective as SPF 25? You will perform an experiment that will help answer that question.

The ultraviolet band is broken into three types, referred to as UVA, UVB, and UVC. The most harmful of these three, UVC light, is absorbed by the atmosphere and does not reach the Earth’s surface. UVB light is responsible for many skin problems, such as sunburns and several forms of skin cancer. UVA light is deep penetrating and causes tanning, wrinkles, and some forms of skin cancer.

In this experiment, you will measure the amount of UVB light that passes through various sunscreens and compare it with the amount of UVB light from direct sun.

Objectives

In this experiment, you will

• Use a UVB Sensor to measure UVB light.
• Determine the amount of UVB light allowed through 5 different sunscreens.
• Analyze the relationship between UVB light and SPF rating.