1. YOU, ME and UV Topics: Light, Ozone, UV, and Nanoparticles Adapted from Dr. Mort Sternheim Modified by M. Cohn STEM Education Institute University of Massachusetts at Amherst

2. Ozone, UV, and Nanoparticles
Objectives
Wave Behavior and the Science of Color
Ozone and ultraviolet light interactions
Nanoparticles and the development of sunscreen
Skin Analysis

3. Sequencing of Major Questions to Pose
1.) What is the sun’s radiation spectrum?
2.) How is the UV portion of the spectrum influenced by ozone in the atmosphere?
3.) How can sunscreen on our skin compare to the role of ozone in the atmosphere?
4.) Are all sunscreens the same?
5.) How does UV exposure vary globally?
6.) Is it possible to see skin damage using analysis with ADI software?

4. Lesson 1: The Electromagnetic Spectrum and Wave Behavior TED Talks video
Question: Is light, itself, consist of a stream of particles or rather a wave of energy emitted from a source?
How do you know?
If we shine a light on a mirror what does it do?
…Through a body of water?
…and Through a prism, what happens?

5. When light strikes an object it can be:
1.) Transmitted - visible light is commonly transmitted through glass. Glass is said to be transparent to this portion of the spectrum.
2.)Reflected: Light bounces back from a surface. It is not transmitted nor absorbed. Substances like these are opaque (do not transmit light)
3.) Absorbed: Energy is resonated within afterwards Example: A bottle of water sitting out in the sun absorbs infrared heat energy on a sunny day, thus heating up energy. Substances like these are known to be opaque (Waves do not simply pass through).

6. Reflection from surfaces
Refraction or bending
Dispertion of light in prisms and diffraction in spectroscopes 

7. Wave Behavior
electromagnetic waves are waves that are capable of traveling through a vacuum, such as outer space. They have both an electric and magnetic component.
Can you name an electromagnetic wave?
 Mechanical waves that require a medium, such as air or water, in order to transport their energy.
Can you name a mechanical wave?
Electromagnetic waves exist with an enormous range of frequencies and wavelengths. This continuous range of frequencies is known as the electromagnetic spectrum

8. The Speed of Light or “C”
The speed of light is defined as the distance that light travels per second.
 299,792,458 m/s.
It constant, and rounded to ≈3.00×108 m/s
To give an idea: it takes roughly 8 minutes for light to reach us from the sun!
If light is transmitted through a transparent substance, the speed DOES change (such as air, water glass). Denser objects slow down the speed of light due to the vibrational energy needed to transport energy within (why a prism works!)

9. The Spectrum represents a range of low energy, low frequency radio waves with long wavelengths up to high energy, high frequency gamma waves with short wavelengths

10. Introductory Vocab
The frequency (f) of a wave is the number of waves to cross a point in 1 second (units are Hertz – cycles/sec or sec-1)
λ is the wavelength- the distance from crest to crest on a wave

12. Ozone, UV, and Nanoparticles
What is Radiation?
Light radiation is often thought of as a wave with a wavelength (l), speed (c), and frequency (f) related by:
Where c = 3.00 x 108 m/s
Equation:
Since c (the speed of light) is constant, the wavelength and frequency are inversely related
This means that light with a short wavelength will have a high frequency and visa versa.
Source:

13. Example Problem
The AM radio band extends from 5.4x105 Hz to 1.7x106 Hz. What are the longest and shortest wavelengths in this frequency range? Formula: At 5.4x105 Hz At 1.7x106 Hz 13

14. Ozone, UV, and Nanoparticles
Why is higher frequency radiation dangerous? energy comes in packets, or “photons”…
The size of an energy packet or photon (E) is determined by the frequency of the radiation (f). (h) is a constant
E  f E f
Radiation with a higher frequency has more energy in each packet
AND the amount of energy in a packet determines how it interacts with our skin

15. Looking at Visible Light (White light) more closely Ex: Stars in Space… what do we know about color?
Q: If all white light travels at the same speed,
how can colors have different levels of energy?
Has to do with: *Wavelength of individual colors of light.
Do all colors have the same wavelength? ____
What does this mean for frequency? Thus for energy?

16. Inquiry Activity: Visible Light Spectrum
1.) Complete Pre-Activity Reading
2.) Each group needs a (1) flashlight, (1) index card, masking tape, (2) prisms
3.) Follow steps 1-3 of the activity making sure to draw your observations from each step in your print out.
4.) Answer the two discussion questions.
5.)Reflection: Is the speed of light altered in a prism? Explain.

17. Light: A topic of Color
What is white? What is black? Why is this apple red?
Key Notes:
1.) When light strikes at object light is :
-Transmitted, absorbed, or reflected
2.)Reflected light, is the only light which reaches your eyes, thus what you see as an objects color
3.) All colors absorbed, and non reflected =black
If none are absorbed , and all reflected= white (ROYGBIV)
4.) Combinations of colored light produce different colors than that of pigments (think art class)

18. The Color of an Opaque Object Explained
Visible light strikes an object as ROYGBIV (all colors)
Not all objects absorb the entire spectrum of ROYGBIV, some frequencies are reflected while others absorbed.
For example:
if an object absorbs all of the frequencies of visible light except for the frequency associated with blue light, then the object will appear blue in the presence of ROYGBIV

19. The Color of a Transparent Object Explained (Stained Glass)
Transparent materials allow 1 or more of the frequencies of visible light to be transmitted through them; The color(s) that is/are not transmitted by such objects, are typically absorbed by them. The color of a transparent object depends upon what color(s) of light is/are incident upon the object and what color(s) of light is/are transmitted through the object.

20. Color by Addition of Light: The mixing, or addition of colors together
Adding or the combination of visible light colors produces different colors than if you were to use paint!
Primary colors:
Red, green, blue
Secondary colors
Cyan, Magenta, Yellow
R + G = Y
R + B = M
G + B = C l
When all primary colors are mixed equally, what color do they produce? _____ 20

21. Check your understanding: In the diagrams, two different primary lights are shown, what color will they produce on the paper?

22. Color by addition with complimentary colors
If any two colors of light that when mixed together in equal amounts produce white are said to be complementary colors of each other.
Ex: The complementary color of red light is cyan.
Why? Cyan light is equal to a mix of blue and green light; (the two other primaries!) blue and green light when added to red light will produce white light.
  What are other complimentary color combos?
1.) Green + Magenta
2.) Blue + Yellow

23. Check your understanding:
. Suppose that light from a magenta spotlight and light from a yellow spotlight are mixed together, will white light be produced? Explain.

24. Color by Subtraction: when the color appearance of an object is determined by beginning with a single color, or mixture of colors, and identifying which color or colors of light are subtracted from the original set.
Involves the use of Pigments Deff: Chemicals that are capable of selectively absorbing one or more frequency of white light are known as pigments.
Example:
If white light is shining on a shirt, really red,
green & blue light is shining on the shirt.
If the shirt absorbs blue light, only red and green light will be reflected from the shirt.
Q: color does the shirt appear (the color(s) reflected only)?

25. Color perceived in reality is due to the presence of visible light and pigments (natural and unnatural)
In the last example, recall we shined white light (R, B, G) on a shirt only capable of absorbing blue light, thus making it yellow in appearance.
The same shirt now has cyan light shining on it during a concert, what color will it appear?!
Step 1: What is cyan a mix of? ____ & _____
Step 2: What is the only color that will be reflected? Draw a picture if it helps!

26. It will appear Green! determine the color of the same shirt if illuminated with other colors of light below. Be sure to begin by determining the primary color(s) of light that are incident upon the object and then subtracting the absorbed color from the incident color(s).

27. Color by Subtraction: Using Pigments
Primary pigment: Cyan,
Magenta, Yellow
Secondary pigment
Red, Blue, Green.
Overall, how does the mixing of primary pigments via subtraction differ from the mixing of primary light via addition? 27

28. Lab: What is Color? (30-40 min) Question Checkpoints:
(1)Reflection, Transmission and Color (2)Light and Color Sheet
Extra help resource: 28

29. Objective 2: The Sun’s radiation spectrum
Ozone, UV, and Nanoparticles
Objective 2: The Sun’s radiation spectrum
Most of the sun’s radiation is Ultraviolet (UV), Visible & Infrared (IR) :
~ 43% is in the visible range
~ 49% is in the near infrared range
~ 7% is in the ultraviolet range
< 1% is x-rays, gamma rays, radio waves
Source: Adapted from

30. Some types of electromagnetic radiation
Ozone, UV, and Nanoparticles
Some types of electromagnetic radiation
The sun emits several kinds of electromagnetic radiation: Visible (Vis), Infrared (IR) and Ultra Violet (UV). Note the split into UVA, UVB, UVC
Each kind is distinguished by a characteristic wavelength, frequency and energy
Higher energy radiation can damage our skin
High Energy Low Energy
Source:

31. Ozone, UV, and Nanoparticles
Skin Damage Explained
Very high UV energy radiation (UVC) is currently blocked by the ozone layer
High energy UV radiation (UVB) does the most immediate damage to skin (sunburns)
But lower energy UV radiation (UVA) can penetrate deeper into the skin, leading to long term damage
Source: N.A. Shaath. The Chemistry of Sunscreens. In: Lowe NJ, Shaath NA, Pathak MA, editors. Sunscreens, development, evaluation, and regulatory aspects. New York: Marcel Dekker; p

32. Discovery Streaming Video: 20:15 You, Me and UV

33. Task: Download UV alert Apps on Phones
For Iphones and Droids: Coppertone MyUVAlert

34. Weekly HW Task: UV Beads Daily Data Log
Each day at about the same time record all information into your log
1.) Take picture of beads after 30 seconds of exposure (close up) with date written on sticky in photo
2.) Record bead color/exposure on number scale given to you
3.) Current UV index using app
4.) Current Weather Conditions (ie: 50% cloudy, rainy, overcast)

35. What other factors do you think contribute to the daily UV index/ UV exposure at ground level?
1.) 2.)
3.)
4.)

36. Part II. Ozone and Ultraviolet Light What is ozone?
Ozone, UV, and Nanoparticles
Part II. Ozone and Ultraviolet Light What is ozone?
Ozone: O3 (3 oxygen atoms)
Ozone is much more reactive, unstable than O or O2
Pale blue, poisonous gas Bad at ground level!
Absorbs ultraviolet radiation! Good!

37. Ozone layer Background
Ozone, UV, and Nanoparticles
Ozone layer Background
Ozone in stratosphere, 10 to 50 km above surface
Ozone Can be depleted by catalysts – NO, OH, Cl, Br – from natural / human sources (CFC’s)
Stratospheric ozone levels decreasing ~4% per year since ’70’s
More skin cancer?
Larger seasonal decrease in lower altitudes (troposphere) in polar regions: the ozone hole
CFC’s phased out globally by 1996 (Montreal Protocol, 1987) – will take decades to leave atmosphere
Ozone levels starting to stabilize
Recovery will take decades

38. Ozone and UV Interaction Cycle
Ozone, UV, and Nanoparticles
Ozone and UV Interaction Cycle
In the stratosphere, ozone absorbs 97+ % of UV
Ozone is produced by solar UVC light from O2 :
O2 + UVC → 2 O (free’s up oxygen in the atm.)
O + O2 → O3
However, zone is also destroyed by UVA/UVB
O3 + UV (with lower energy) → O2 + O

40. Essential Question
Why are ozone levels depleting if ozone is normally destroyed by UVB/UVA and then Created by UVC?
Other Compounds such as CFC’s are also causing Ozone to break down, while there is a relatively finite amount of UV radiation that reaches the stratosphere daily
For More Information visit

41. Ozone Varies Globally- measured in Dobsen Units which show how THICK the layer is

42. Ozone variations by latitude and season: Ozone thins with increase of pollutants in atmosphere and in S.H. colder temp’s but only in the presence of sunlight

43. Lesson II: First Student Centered Investigation: What effects UV radiation that reaches surface?
Task:
To link any connections between global UV indexes and daily ozone thickness (concentration) in the upper atmosphere at a minimum of 5 locations using ozone maps and uv index records.
This is a student centered investigation. You will be researching REAL data from archives to come to a conclusion.
The document can be opened under student resources to make the links active.
Your document is to be typed as a lab report with an introduction, body containing data, and conclusion.

44. Your Resources
Ozone thickness maps global:
*Note that this map has more defined data but its rare that current maps are available and you must pick prior dates Today’s Ozone Thickness Map (Global):
US UV indexes by location DAILY:
US UV indexes archive for PAST dates:
-Global UV indexes by location:

45. Part III: Science Behind Suncreen Are all Sunscreen’s the same
Part III: Science Behind Suncreen Are all Sunscreen’s the same? The introduction of Nano Technology!

46. A Brief History of Sunscreens: The Beginning
Ozone, UV, and Nanoparticles
A Brief History of Sunscreens: The Beginning
First developed for soldiers in WWII (1940s) to block “sunburn causing rays”
These were called UVB rays
WWII soldier in the sun
Shorter wavelengths (more energy) called UVC
Longer wavelengths (less energy) called UVA
Sources:

47. A Brief History of Sunscreens: The SPF Rating
Ozone, UV, and Nanoparticles
A Brief History of Sunscreens: The SPF Rating
Sunscreens first developed to prevent sunburn
Ingredients were good UVB blockers
SPF (Sunscreen Protection Factor) Number
Measures the strength of UVB protection only
Higher SPF # = more protection from UVB
Doesn’t tell you anything about protection from UVA!!!
UVA causes cancer, skin aging
No official UVA ratings until now
Sources: and

48. Zinc: Works as an agent to block BOTH UVA and UVB Why don’t people use this if it’s the best protection?

49. Know Your Sunscreen: Look at the Ingredients
Ozone, UV, and Nanoparticles
Know Your Sunscreen: Look at the Ingredients
UV blocking agents suspended in a lotion
“Colloidal suspension”
Two kinds of active ingredients
Organic ingredients and inorganic ingredients
Lotion has “inactive ingredients”
Don’t block UV light
UV blocking agents are “active ingredients”
Usually have more than one kind present
Source: Original Image

50. How does absorption of light by inorganic compounds differ from absorption by organic molecules?

51. Organic Ingredients: The Basics
Ozone, UV, and Nanoparticles
Organic Ingredients: The Basics
Organic = Carbon Atoms
Hydrogen, oxygen & nitrogen atoms are also often involved
Structure
Covalent bonds
Exist as individual molecules
Size
Molecular formula determines size
Typically < 10 nm
Octyl methoxycinnamate (C18H26O3)
an organic sunscreen ingredient
Sources: and original image

52. Organic Ingredients: UV Absorption
Ozone, UV, and Nanoparticles
Organic Ingredients: UV Absorption
Electrons capture the energy from UV rays
They jump to higher energy levels
The energy is released as infrared (heat) rays which are harmless (each ray is low in energy)
Problem: Will not absorb the whole UV spectrum, just UVB!  BUT they do not SCATTER light so organic sunscreens do not appear white.
hf=2.48 eV
3hf=2.48 eV
Source: Adapted from

53. Inorganic Ingredients: The Basics
Ozone, UV, and Nanoparticles
Inorganic Ingredients: The Basics
Atoms: Zinc or Titanium, Oxygen
Structure
Ionic molecules: ZnO, TiO2
Cluster of ions
Formula unit doesn’t dictate size
Cluster (particle) size
Varies with # of ions in cluster
~10 nm – 300 nm
Absorb thru whole UV spectrum up to 380 nm
Detail of the ions in one cluster
Group of TiO2 particles
Source: and image adapted from

54. Ozone, UV, and Nanoparticles
Why not use inorganics?
Appearance Matters
Traditional inorganic sunscreens have appeared white on our skin (large molecules)
Many people don’t like how this looks, so they don’t use sunscreen with inorganic ingredients
Of the people who do use them, most apply too little to get full protection
Source:

55. Why Do They Appear White?
Ozone, UV, and Nanoparticles
Why Do They Appear White?
Traditional ZnO and TiO2 clusters are large
(> 200nm)
Large clusters scatter visible light
( nm)
Maximum scattering occurs for wavelengths twice as large as the clusters
The scattered light is reflected to our eyes, appearing white…and looking bad!
Source: Original image

56. Size ranges of particles

57. 2. Nanoparticles and sunscreen
Ozone, UV, and Nanoparticles
2. Nanoparticles and sunscreen
Nanoparticles: 1 to 100 nm in diameter, or about 10 to 1000 atomic diameters
Number of products using nanomaterials is growing very rapidly
Clothing, food and beverages, sporting goods, coatings, cosmetics, personal care, electronics
Sunscreens: many use nanomaterials
Some labeled as containing nanoparticles
Some not labeled
The smaller the particle…the shorter the wavelength of light will be that it scatters.

58. Nanosized Inorganic Clusters
Ozone, UV, and Nanoparticles
Nanosized Inorganic Clusters
Maximum scattering occurs for wavelengths twice as large as the clusters (particle size)
Make the clusters smaller (100 nm or less) and they won’t scatter visible light (which is what makes sunscreen appear white)
Source: Graph adapted from

59. In summary…How sunscreen works
Sunscreen works by combining organic and inorganic active ingredients.
Inorganic ingredients like zinc oxide or titanium oxide reflect or scatter ultraviolet (UV) radiation.
Organic ingredients like octyl methoxycinnamate (OMC) or oxybenzone absorb UV radiation, dissipating it as heat.
Some sunscreens protect us from the two types of damaging UV radiation: UV-A and UV-B Both UV-A and UV-B cause sunburns and damaging effects such as skin cancer.
Broad Spectrum= protects against both forms

60. Ozone, UV, and Nanoparticles
In Summary…
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
Source:

61. Ozone, UV, and Nanoparticles
New FDA UVA Ratings (2012)
The phrase “broad spectrum” is meant to indicate protection against UVA
Products labeled “broad spectrum” will have to provide equal protection against UVB and UVA
Bathing suits: 3 tbsp every 2 hours

62. Skin Cancer Rates are Rising Fast
Ozone, UV, and Nanoparticles
Skin Cancer Rates are Rising Fast
Probability of getting skin cancer:
1930 : 1 in 5,000
2004 : 1 in 65
2050 : 1 in 10…
Skin cancer:
Is ~50% of all cancer cases
Has > 1 million cases diagnosed each year
Causes 1 person to die every hour
Causes of the increase:
Decreased ozone protection
Increased time in the sun
Increased use of tanning beds
Sources: ;

63. Complete Post Lesson Questions

64. PART IV Investigation: Testing Sunscreen and UV Absorption
Ozone, UV, and Nanoparticles
PART IV Investigation: Testing Sunscreen and UV Absorption
Use UV sensitive beads
Compare opacity/ transparency of samples for visible light and UV light including their claim on SPF ratings
Beads absorb UV from 300 nm to 360 nm (UV A is 320 – 400 nm, UV B is 280 – 320 nm)
Class will report on which suncreen worked the most efficiently –list active ingredients

65. Teacher note highlights
Ozone, UV, and Nanoparticles
Teacher note highlights
Safety. Do not look directly at the UV lamp
Liquids. Apply directly to bead or to clear plastic strips
Purchasing. See teacher notes handout
Making the testers. Melt beads in oven, glue to sticks

66. Ozone, UV, and Nanoparticles
Available documents
Handouts
More on the website
This PowerPoint
Teacher guide
Student write-up
Consumer Reports sunscreen ratings
UV violet color guide
Controlled Experiment On The Transmission Of Ultra-Violet Radiation (Jennifer)
Web links
UVA standards articles
Sunscreen clothing – does it work?

67. Skin Cancer
Skin Cancer info
history channel skin damge (1.5 min)

68. ADI Surface Skin Analysis for UVB using unevenness in Red vs
ADI Surface Skin Analysis for UVB using unevenness in Red vs. Green intensities