Sunscreens

Question 1

Explain the sunscreen chemistry in three short steps

Answer 1

Incoming UV radiation
Excited molecule
Outgoing radiation

Question 2

What are some good effects of sunlight?

Answer 2

Warmth
Kills pathogens
Vision
Vitamin D synthesis
Photosynthesis
Phototherapy

Question 3

What are some bad effects of sunlight?

Answer 3

Sunburn
Pre-mature ageing
Cancer
Pre-cancer
Cataracts
Photosensitivity
Immune system changes

Question 4

In the UK, ____ people a year die from malignant melanoma, and the number is increasing.

Answer 4

2,000

Question 5

What SPF should someone use?

Answer 5

• at least SPF 15
• the higher the better
• broad-spectrum sunscreen; protects against harmful UVA and UVB rays

Question 6

Most sunscreens have a shelf life of

Answer 6

2-3 years

Question 7

When should you use water resistant sun screen?

Answer 7

If sweating/ contact with water is likely

Question 8

Broad-spectrum products provide protection against the sun’s UVB and UVA rays. The sun protection factor, or SPF, is a measurement of the amount of UV_ protection. The higher the number, the greater the protection. In the UK, UV_ protection is measured with a ___ rating. Sunscreens has from 0 to 5 stars. The higher the number of stars, the greater the protection.

Answer 8

B
A
star

Question 9

TYPE 1 SKIN TYPE MEANS

Answer 9

Always burns easily; never tans

Question 10

TYPE 2 SKIN TYPE MEANS

Answer 10

Always burns easily; tans minimally

Question 11

TYPE 3 SKIN TYPE MEANS

Answer 11

Burns moderately; tans gradually

Question 12

TYPE 4 SKIN TYPE MEANS

Answer 12

Burns minimally; always tans well

Question 13

TYPE 5 SKIN TYPE MEANS

Answer 13

Rarely burns; tans profusely

Question 14

TYPE 6 SKIN TYPE MEANS

Answer 14

Never burns; deeply pigmented

Question 15

Molecules go from ground state to excited state to ground state. Energy is given off as:

Answer 15

IR
Visible
Cis/ trans isomerisation
Fluorescence

Question 16

Absorption range and peak for organic sunscreen?

Answer 16

255nm - 345nm

Peak at 310.

Question 17

Absorption range and peak for inorganic sunscreen?

Answer 17

Consistent UV absorption upto 380nm

Question 18

Name a sunscreen that blocks both UVA and UVB

Answer 18

Zinc Oxide/ Titanium Oxide

Question 19

Name 2 sunscreens that blocks all of UVA and quarter UBV

Answer 19

Avobenzone

Ecamsule

Question 20

Name a sunscreen that blocks UVB only

Answer 20

homosalate

PABA

Question 21

Advantages and examples of metal oxides?

Answer 21

Zinc Oxide
Titanium Oxide

Super water resistant
Microsized so it isn’t visible

Question 22

Why do inorganic sunscreens appear white?

Answer 22

Titanium and Zinc Oxide clusters are large (>200nm).
Large clusters can scatter light in many different directions
Maximum scattering occurs for wavelengths twice as large as the cluster
l > 400 nm
This is visible light!