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Topics for Today. UV-B and UV-C Sunscreen and the Ozone Layer!. Readings for Today. What is the difference between UV-A, UV-B, and UV-C?. Section 2.4 Waves of Light Section 2.6 The oxygen / ozone sunscreen Section 2.7 Biological Effects of Radiation!. Topics for Wednesday.
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Topics for Today • UV-B and UV-C • Sunscreen and the Ozone Layer!
Readings for Today What is the difference between UV-A, UV-B, and UV-C? Section 2.4 Waves of Light Section 2.6 The oxygen / ozone sunscreen Section 2.7 Biological Effects of Radiation!
Topics for Wednesday • The Ozone Hole
Readings for Wednesday Section 2.8 Stratospheric Ozone Destruction Section 2.9 CFCs (the first part (page 92-93) about their uses) Section 2.10 The Antarctic Ozone Hole: A Closer Look
Readings for Friday • What’s in a bond? Seeing Electrons Section 2.3 H H . . : : H C H C H H . . H H
Topics for Today • UV-B and UV-C • Sunscreen and the Ozone Layer!
Fluorescence A two-step process!! 1) Incoming wavelength is absorbed 2) Light of a LOWER energy is re-emitted
ULTRAVIOLET RADIATION UV-C UV-B UV-A 200 nm 280 nm 320 nm 400 nm Higher or lower energy than UV-A?
ULTRAVIOLET RADIATION UV-C UV-B UV-A 200 nm 280 nm 320 nm 400 nm HIGHER
ULTRAVIOLET RADIATION UV-C UV-B UV-A 200 nm 280 nm 320 nm 400 nm UV-B is more damaging
UV-B Penetrates little into the skin
Why less penetration than UV-A? • UV-B Penetrates little into the skin
It gets absorbed! • UV-B Penetrates little into the skin
UV-B Needed to synthesize Vitamin D3 in your body
Vitamin D3 - Regulates the absorption of calcium in your bones.
Vitamin D3 Synthesized in your epidermis in the presence of UV-B (290 – 320 nm)
UV-B Responsible for sunburn
Look at the scale! 10 times less dangerous 1000 times less dangerous Figure 2.13 page 83 100,000 times less dangerous
UV-B Responsible for skin cancer Can break bonds in DNA!
Twice as many deaths due to melanomas are seen in the southern states of Texas and Florida, as in the northern states of Wisconsin and Montana (relative to the population size)
Twice as many deaths due to melanomas are seen in the southern states of Texas and Florida, as in the northern states of Wisconsin and Montana (relative to the population size) What’s melanoma?
Twice as many deaths due to melanomas are seen in the southern states of Texas and Florida, as in the northern states of Wisconsin and Montana (relative to the population size) What is another melanoma risk factor? What’s melanoma?
Incidence of melanoma skin cancer in the U.S. 1973-1998 Source: the National Cancer Institute Figure 2.14 page 85
Do sunscreens protect us from UV-B?? Incidence of melanoma skin cancer in the U.S. 1973-1998 Source: the National Cancer Institute Figure 2.14 page 85
UV-B UV-A Octinoxate (5.25%) UV-B UV-B
Does our atmosphere protect us from UV-B?? Incidence of melanoma skin cancer in the U.S. 1973-1998 Source: the National Cancer Institute Figure 2.14 page 85
YES!! Sort of.
ULTRAVIOLET RADIATION UV-C UV-B UV-A 200 nm 280 nm 320 nm 400 nm O3 O2 + O. λ< 320 nm
UV-B 30 miles O3 O2 + O. 15 miles UV-B
DEMO! OZONE SHADOW
Ozone absorbs UV-B light Does ozone absorb UV-A?
ULTRAVIOLET RADIATION UV-C UV-B UV-A 200 nm 280 nm 320 nm 400 nm O3 O2 + O. λ< 320 nm
Above the atmosphere Fig. 2.12 At the surface
Our body responds differently to ALL types of UV radiation! How is UV-A different from UV-B?
ULTRAVIOLET RADIATION UV-C UV-B UV-A 200 nm 280 nm 320 nm 400 nm
ULTRAVIOLET RADIATION UV-C UV-B UV-A 200 nm 280 nm 320 nm 400 nm Higher or lower energy than UV-B?
ULTRAVIOLET RADIATION UV-C UV-B UV-A 200 nm 280 nm 320 nm 400 nm Most damaging of all UV radiation! Higher or lower energy than UV-B?
UV-C Used to kill airborne bacteria
UV-C • Used to sterilize medical equipment (germicide)
Miles Can our atmosphere protect us from UV-C? Miles http://www.windows.ucar.edu/earth/images/atmosphere_mural.jpg
ULTRAVIOLET RADIATION UV-C UV-B UV-A 200 nm 280 nm 320 nm 400 nm
UV-C does NOT make it to the earth’s surface! ULTRAVIOLET RADIATION UV-C UV-B UV-A O3 O2 + O. λ< 320 nm 200 nm 280 nm 320 nm 400 nm O2 2O. λ<242 nm
UV-C 30 miles O3 O2 + O. 15 miles
Summary Not all UV is created equal! UV light gets to the surface in different proportions! May be a good exam question… Why??
Review: What about the other types of electromagnetic radiation?
What happens when molecules absorb light? It depends on the wavelength (λ).