Skills Worksheet - Madison County School District



Skills Worksheet REAL WORLD APPLICATIONS

Cross-Disciplinary

How Does Sunscreen Work?

Read the following paragraphs, and complete the exercises below.

Have you ever wondered how the sun’s rays can cause sunburns and suntans? When too much ultraviolet (UV) radiation from the sun strikes your skin, small vessels in the skin expand. These vessels contain groups of red and white blood cells, which produce the red coloring that is known as a sunburn.

The body’s defense against sunburn is to release a chemical pigment, called melanin, to the surface of the skin. Melanin absorbs UV radiation from the sun, preventing it from penetrating the skin tissue. The melanin also causes the dark coloring that we call a suntan. When the melanin cells die, the suntan fades.

Sunscreens work like melanin

LIKE MELANIN, SUNSCREENS CONTAIN PIGMENTS THAT ABSORB UV RADIATION FROM THE SUN TO KEEP IT FROM PENETRATING THE SKIN. THE SPF OF A SUNSCREEN TELLS HOW MUCH RADIATION IT ABSORBS. FOR EXAMPLE, SPF 10 ABSORBS ALL BUT 1/10 OF THE SUN’S ULTRAVIOLET RADIATION, WHILE SPF 40 ABSORBS ALL BUT 1/40 OF IT.

SPF ratings are only approximate because they depend on how much sunscreen you apply. People with light complexions have less melanin pigment. As a result, they must use higher levels of SPF to be protected from the sun’s ultraviolet rays.

Exercises

1. WHAT CAUSES SUNBURNS AND SUNTANS?

2. How are the pigments in sunscreen similar to melanin?

3. Suppose you are wearing sunscreen with SPF 20. How much of the sun’s UV radiation will be absorbed by the sunscreen? How much will penetrate your skin?

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