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Ultraviolet Waves Learning Objectives 1.To understand that ultraviolet waves can cause suntan and sunburn 2.To understand how to protect yourself from.

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Presentation on theme: "Ultraviolet Waves Learning Objectives 1.To understand that ultraviolet waves can cause suntan and sunburn 2.To understand how to protect yourself from."— Presentation transcript:

1 Ultraviolet Waves Learning Objectives 1.To understand that ultraviolet waves can cause suntan and sunburn 2.To understand how to protect yourself from sunburn We are now concentrating on ultraviolet waves which has more energy than visible light Increasing frequency hence Increasing energy

2 UV Waves Ultraviolet waves have a number of everyday uses including forgery detection and optical brighteners in washing powder. However the greatest source of UV is from our sun.

3 UV & Humans : Suntans Much of the UV from the sun is currently blocked by the Ozone layer (more later). When human skin is exposed to UV the skin produces a pigment called melanin which results in a suntan Tanned skin absorbs the radiation so the UV does not reach the lower layers causing sunburn and skin caner

4 UV & Humans : Sunburn To much exposure to the UV in sunlight initially causes painful sunburn

5 UV & Humans : Sunburn To much exposure to the UV in sunlight initially causes painful sunburn

6 UV & Humans : Skin Cancer Regular overexposure to the UV in sunlight can cause early skin aging & lead to skin cancer which can prove fatal

7 UV & Humans : Skin Cancer

8 Protecting against UV The easiest way to avoid sunburn and other skin damage is to take the following precautions Stay out of the sun at midday Stay in the shade Cover up : clothes & wide brimmed hats Limit time in the sun until tan develops Apply a high factor sunscreen

9 Protecting against UV

10 Sun Index A measure of how strong/burning the strength of the sun is Sun IndexRisk 1-2Low risk 3-4Avoid being in the sun for more than 1- 2 hours 5-6Burns in 30-60mins 7-10Severe burns in 20-30mins These times are for someone with untanned white skin who burns easily

11 Sun Protection Factor (SPF) The Sun Protection Factor (SPF) is a measure of how much protection a particular sun cream offers... How much longer you can stay in the sun without a risk of burning Safe time in sun with cream = SPF xtime given by sun index

12 SPF Worked example If the weather forecast predicts that the sun index will be 7 what is the longest time an untanned white person can stay in the sun if they correctly apply sun cream with SPF 15? Safe time in sun with cream = SPF xtime given by sun index Safe time in sun with cream = 15 x 30 Safe time in sun with cream = 450 mins


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