1. Sun Protection
How it Works

2. SPF factor and sun tanning Take notes from the ppt to answer the
following questions:
What does SPF stand for?
How do UVA rays differ from UVB rays?
What does SPF on sunscreen indicate?
What should you consider when using a sunscreen?
How much sunscreen should you apply?

3. SPF SPF stands for Sun Protection Factor
The SPF rating system was developed in 1962 by Franz Greiter.
The SPF rating system applies to UVB rays, the rays responsible for sunburn.

4. UVA Rays UVA - UV rays that have the longest wavelength.
UVA rays account for up to 95% of the UV radiation reaching the Earth’s surface and damage skin by penetrating deeper than UVB rays. UVA rays cause skin cancer and wrinkles.
Tanning booths primarily emit UVA rays.
There is currently no approved SPF rating system that measures UVA rays.

5. UVB Rays UVB - UV rays that have shorter wavelengths than UVA rays.
UVB rays damage the skin’s more superficial layers. The intensity of these rays varies by season, location, and time of day (the most significant amount hits the U.S. between 10 am - 4 pm from April to October).

6. Sunscreens
SPF indicates how long it will take for UVB rays to redden skin when using a sunscreen, compared to how long skin would take to redden without the product. Example: Someone using a sunscreen with an SPF of 30 will take 30 times longer to redden than without the sunscreen.
You need protection from both kinds of rays. Look for a sunscreen with an SPF of 15 or higher, plus some combination of the following UVA-screening ingredients: stabilized a avobenzone, ecamsule (a.k.a. Mexoryl), oxybenzone, titanium dioxide, and zinc oxide. You may see the phrases multi spectrum, broad spectrum or UVA/UVB protection on sunscreen labels, and these all indicate that some UVA protection is provided. However, because there is no consensus on how much protection these terms indicate, such phrases may not be entirely meaningful.
You should apply 1 ounce (2 tablespoons) of sunscreen to your entire body 30 minutes before going outside. Reapply every two hours, or immediately after swimming or excessive sweating.

7. Sunprint Paper from the Sunscreen Lab
SPF 0
SPF 4
SPF 8
SPF 15
SPF 45
Unknown