Topics for Today

1. Topics for Today • UV-B and UV-C • Sunscreen and the Ozone Layer!

2. 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!

3. Topics for Wednesday • The Ozone Hole

4. 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

5. Readings for Friday • What’s in a bond? Seeing Electrons Section 2.3 H H . . : : H C H C H H . . H H

6. Topics for Today • UV-B and UV-C • Sunscreen and the Ozone Layer!

7. Fluorescence A two-step process!! 1) Incoming wavelength is absorbed 2) Light of a LOWER energy is re-emitted

8. ULTRAVIOLET RADIATION UV-C UV-B UV-A 200 nm 280 nm 320 nm 400 nm Higher or lower energy than UV-A?

9. ULTRAVIOLET RADIATION UV-C UV-B UV-A 200 nm 280 nm 320 nm 400 nm HIGHER

10. ULTRAVIOLET RADIATION UV-C UV-B UV-A 200 nm 280 nm 320 nm 400 nm UV-B is more damaging

11. UV-B Penetrates little into the skin

12. Why less penetration than UV-A? • UV-B Penetrates little into the skin

13. It gets absorbed! • UV-B Penetrates little into the skin

14. UV-B Needed to synthesize Vitamin D3 in your body

15. Vitamin D3 - Regulates the absorption of calcium in your bones.

16. Vitamin D3 Synthesized in your epidermis in the presence of UV-B (290 – 320 nm)

17. UV-B Responsible for sunburn

18. Look at the scale! 10 times less dangerous 1000 times less dangerous Figure 2.13 page 83 100,000 times less dangerous

19. UV-B Responsible for skin cancer Can break bonds in DNA!

20. 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)

21. 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?

22. 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?

23. Incidence of melanoma skin cancer in the U.S. 1973-1998 Source: the National Cancer Institute Figure 2.14 page 85

24. 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

25. UV-B UV-A Octinoxate (5.25%) UV-B UV-B

26. 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

27. YES!! Sort of.

28. ULTRAVIOLET RADIATION UV-C UV-B UV-A 200 nm 280 nm 320 nm 400 nm O3 O2 + O. λ< 320 nm

29. UV-B 30 miles O3 O2 + O. 15 miles UV-B

30. DEMO! OZONE SHADOW

31. Ozone absorbs UV-B light Does ozone absorb UV-A?

32. ULTRAVIOLET RADIATION UV-C UV-B UV-A 200 nm 280 nm 320 nm 400 nm O3 O2 + O. λ< 320 nm

33. Above the atmosphere Fig. 2.12 At the surface

34. Our body responds differently to ALL types of UV radiation!

35. Our body responds differently to ALL types of UV radiation! How is UV-A different from UV-B?

37. ULTRAVIOLET RADIATION UV-C UV-B UV-A 200 nm 280 nm 320 nm 400 nm

38. ULTRAVIOLET RADIATION UV-C UV-B UV-A 200 nm 280 nm 320 nm 400 nm Higher or lower energy than UV-B?

39. 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?

40. UV-C Used to kill airborne bacteria

41. UV-C • Used to sterilize medical equipment (germicide)

42. Miles Can our atmosphere protect us from UV-C? Miles http://www.windows.ucar.edu/earth/images/atmosphere_mural.jpg

43. ULTRAVIOLET RADIATION UV-C UV-B UV-A 200 nm 280 nm 320 nm 400 nm

44. 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

45. UV-C 30 miles O3 O2 + O. 15 miles

46. Summary Not all UV is created equal! UV light gets to the surface in different proportions! May be a good exam question… Why??

47. Our Atmospheric Blanket

48. Review: What about the other types of electromagnetic radiation?

49. What happens when molecules absorb light? It depends on the wavelength (λ).

50. What happens when α molecule absorbs light?