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

• Whats in a bond? Seeing Electrons Section 2.3

H
H
. .


C
H
C
H
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-A
UV-B
UV-C
200 nm
400 nm
320 nm
280 nm
Higher or lower energy than UV-A?
9
ULTRAVIOLET RADIATION
UV-A
UV-B
UV-C
200 nm
400 nm
320 nm
280 nm
HIGHER
10
ULTRAVIOLET RADIATION
UV-A
UV-B
UV-C
200 nm
400 nm
320 nm
280 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)
Whats 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?
Whats 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
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-A
UV-B
UV-C
200 nm
400 nm
320 nm
280 nm

• O3 O2 O.
• ?lt 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-A
UV-B
UV-C
200 nm
400 nm
320 nm
280 nm

• O3 O2 O.
• ?lt 320 nm

33
Absorbance Spectrum of Ozone
34
Above the atmosphere
At the surface

• Fig. 2.12

35

• Our body responds differently to ALL types of UV
  radiation!

36

• Our body responds differently to ALL types of UV
  radiation!

How is UV-A different from UV-B?
37
(No Transcript)
38
ULTRAVIOLET RADIATION
UV-A
UV-B
UV-C
200 nm
400 nm
320 nm
280 nm
39
ULTRAVIOLET RADIATION
UV-A
UV-B
UV-C
200 nm
400 nm
320 nm
280 nm
Higher or lower energy than UV-B?
40
ULTRAVIOLET RADIATION
UV-A
UV-B
UV-C
200 nm
400 nm
320 nm
280 nm
Most damaging of all UV radiation!
Higher or lower energy than UV-B?
41

• UV-C
• Used to kill airborne bacteria

42

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

43
Miles
Can our atmosphere protect us from UV-C?
Miles
http//www.windows.ucar.edu/earth/images/atmospher
e_mural.jpg
44
ULTRAVIOLET RADIATION
UV-A
UV-B
UV-C
200 nm
400 nm
320 nm
280 nm
45
UV-C does NOT make it to the earths surface!
ULTRAVIOLET RADIATION
UV-A
UV-B
UV-C

• O3 ? O2 O.
• ?lt 320 nm

200 nm
400 nm
320 nm
280 nm
O2 ? 2O.
?lt242 nm
46
UV-C
30 miles
O3 ? O2 O.
15 miles
47
Summary

• Not all UV is created equal!
• UV light gets to the surface in different
  proportions!

May be a good exam question
Why??
48
Our Atmospheric Blanket
49
Review What about the other types of
electromagnetic radiation?
50
What happens when molecules absorb light?
It depends on the wavelength (?).
51
What happens when a molecule absorbs light?
52

Ionizing radiation
e-


H2O
H2O.
53
(No Transcript)
54

• O2 O. O.
• ?lt 242 nm
• O3 O2 O.
• ?lt 320 nm

55
(No Transcript)
56

• Visible light can break bonds, but the bond must
  be pretty weak.

57
Visible light 600 nm

Visible light 600 nm

O.
NO2
NO
58
(No Transcript)
59
(No Transcript)
60
Topics for Wednesday

• The Ozone Hole

61
Miles
Miles
http//www.windows.ucar.edu/earth/images/atmospher
e_mural.jpg
62
Miles
Miles
http//www.windows.ucar.edu/earth/images/atmospher
e_mural.jpg
63
Ozone concentration depends on altitude!

• Fig. 2.1, Chemistry in Context

64
Ozone concentration also depends on where you are
on the earth!
65
(No Transcript)
66
Ozone concentration in a column of air above your
head!
67
What is a D.U.?
68
Dobson Unit
1 D.U. 1 Dobson Unit 1 ppb ozone
69
How do we measure ozone in the atmosphere?
70
Lab This Week!!
71
Satellites!
http//toms.gsfc.nasa.gov/eptoms/ep_v8.html
72
Measures 6 wavelengths from 300-350 nm
Why are these ? important for ozone?
? lt 320 nm
O3 ? O2 O.
UV-A
UV-B
UV-C
200 nm
400 nm
320 nm
280 nm
73
Pictures!
74
(No Transcript)
75
(No Transcript)
76
(No Transcript)
77
(No Transcript)
78
(No Transcript)
79
(No Transcript)
80
How long does the ozone hole last?
81
(No Transcript)
82
(No Transcript)
83
(No Transcript)
84
Until early December
How long does the ozone hole last?
85
(No Transcript)
86
http//toms.gsfc.nasa.gov/eptoms/ep_ovplist_a.html
Ozone Levels (January 1)
87
(No Transcript)