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PY352 > Sunscreens > Flashcards

Sunscreens Flashcards

1
Q

Explain the sunscreen chemistry in three short steps

A

Incoming UV radiation
Excited molecule
Outgoing radiation

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2
Q

What are some good effects of sunlight?

A 
Warmth
Kills pathogens
Vision
Vitamin D synthesis
Photosynthesis
Phototherapy
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3
Q

What are some bad effects of sunlight?

A 
Sunburn
Pre-mature ageing
Cancer
Pre-cancer
Cataracts
Photosensitivity
Immune system changes
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4
Q

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

A

2,000

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5
Q

What SPF should someone use?

A
  • at least SPF 15
  • the higher the better
  • broad-spectrum sunscreen; protects against harmful UVA and UVB rays
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6
Q

Most sunscreens have a shelf life of

A

2-3 years

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7
Q

When should you use water resistant sun screen?

A

If sweating/ contact with water is likely

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8
Q

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.

A

B
A
star

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9
Q

TYPE 1 SKIN TYPE MEANS

A

Always burns easily; never tans

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10
Q

TYPE 2 SKIN TYPE MEANS

A

Always burns easily; tans minimally

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11
Q

TYPE 3 SKIN TYPE MEANS

A

Burns moderately; tans gradually

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12
Q

TYPE 4 SKIN TYPE MEANS

A

Burns minimally; always tans well

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13
Q

TYPE 5 SKIN TYPE MEANS

A

Rarely burns; tans profusely

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14
Q

TYPE 6 SKIN TYPE MEANS

A

Never burns; deeply pigmented

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15
Q

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

A

IR
Visible
Cis/ trans isomerisation
Fluorescence

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16
Q

Absorption range and peak for organic sunscreen?

A

255nm - 345nm

Peak at 310.

17
Q

Absorption range and peak for inorganic sunscreen?

A

Consistent UV absorption upto 380nm

18
Q

Name a sunscreen that blocks both UVA and UVB

A

Zinc Oxide/ Titanium Oxide

19
Q

Name 2 sunscreens that blocks all of UVA and quarter UBV

A

Avobenzone

Ecamsule

20
Q

Name a sunscreen that blocks UVB only

A

homosalate

PABA

21
Q

Advantages and examples of metal oxides?

A

Zinc Oxide
Titanium Oxide

Super water resistant
Microsized so it isn’t visible

22
Q

Why do inorganic sunscreens appear white?

A

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!

PY352 (25 decks)

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