Water wave (ripple tank) simulation: http://www.falstad.com/ripple/
What could we do to inorganic clusters to prevent them from scattering visible light?
Source: Adapted from http://www.loc.gov/rr/scitech/mysteries/images/sunscreen2.jpg
Source: Graph adapted from http://www.aims.gov.au/pages/research/projects/sunscreens/pages/sunscreens02.html
Maximum scattering occurs for wavelengths twice as large as the clusters
Make the clusters smaller (100 nm or less) and they won’t scatter visible light
Nano-Sunscreen Appears Clear
Three sunscreens were tested for scattering with different wavelengths of light
One contains nanosized inorganic ingredients
One contains traditional inorganic ingredients
One contains organic ingredients
Can you answer these three questions:
Which one is which and how do you know?
Will each one appear white or clear on your skin?
What size (approximately) are the clusters in each sunscreen?
Light Scattering by Three Sunscreens
Nanoparticle sunscreen ingredients are small inorganic clusters that:
Provide good UV protection by absorbing both UVB and UVA light
Appear clear on our skin because they are too small to scatter visible light
What are the most important factors to consider in choosing a sunscreen?
How do you know if a sunscreen has “nano” ingredients?
How do “nano” sunscreen ingredients differ from other ingredients currently used in sunscreens?