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Comparing Sunscreens

Experiment #21 from Earth Science with Vernier


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. UVA light is deep-penetrating and causes tanning, wrinkles, and some forms of skin cancer. UVB light is also responsible for many skin problems such as sunburns and several forms of skin cancer.

In this experiment, you will measure the amount of UV light that passes through various sunscreens. You will then compare it with the amount of UV light from direct sun and analyze the relationship between them.


  • Use a Go Direct Light and Color Sensor to measure UV light.
  • Determine the amount of UV light allowed through five different sunscreens.
  • Analyze the trend of UV light vs. SPF values.

Sensors and Equipment

This experiment features the following sensors and equipment. Additional equipment may be required.

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This experiment is #21 of Earth Science with Vernier. The experiment in the book includes student instructions as well as instructor information for set up, helpful hints, and sample graphs and data.

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Earth Science with Vernier