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

Ultraviolet WavesUltraviolet WavesLearning ObjectivesLearning Objectives

1.1.To understand that To understand that ultraviolet waves can cause ultraviolet waves can cause suntan and sunburnsuntan and sunburn2.2.To understand how to To understand how to protect yourself from protect yourself from sunburnsunburn

We are now concentrating on ultraviolet waves which We are now concentrating on ultraviolet waves which has has more energy than visible lightmore energy than visible light

Increasing frequency henceIncreasing frequency henceIncreasing energyIncreasing energy

UV WavesUV Waves

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

UV & HumansUV & Humans : Suntans: SuntansMuch of the UV from the sun is currently Much of the UV from the sun is currently blocked by the Ozone layer (more later).blocked by the Ozone layer (more later).

When human skin is exposed to UV the skin When human skin is exposed to UV the skin produces a pigment called produces a pigment called melaninmelanin which which results in a suntanresults in a suntan

Tanned skin absorbs the radiation so the UV Tanned skin absorbs the radiation so the UV does not reach the lower layers causing sunburn does not reach the lower layers causing sunburn and skin canerand skin caner

UV & Humans : UV & Humans : SunburnSunburnTo much exposure to the UV in sunlight initially To much exposure to the UV in sunlight initially causes painful causes painful sunburnsunburn

UV & Humans : UV & Humans : SunburnSunburnTo much exposure to the UV in sunlight initially To much exposure to the UV in sunlight initially causes painful causes painful sunburnsunburn

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

UV & Humans : UV & Humans : Skin CancerSkin Cancer

Protecting against UVProtecting against UVThe easiest way to avoid sunburn and other The easiest way to avoid sunburn and other skin damage is to take the following skin damage is to take the following precautionsprecautions

Stay out of the sun at middayStay out of the sun at midday

Stay in the shadeStay in the shade

Cover up : clothes & wide brimmed hatsCover up : clothes & wide brimmed hats

Limit time in the sun until tan developsLimit time in the sun until tan develops

Apply a high factor sunscreenApply a high factor sunscreen

Protecting against UVProtecting against UV

Sun IndexSun IndexA measure of how strong/burning the strength A measure of how strong/burning the strength of the sun isof the sun is

Sun Index Risk

1-2 Low risk

3-4 Avoid being in the sun for more than 1-2 hours

5-6 Burns in 30-60mins

7-10 Severe burns in 20-30mins

These times are for someone with untanned These times are for someone with untanned white skin who burns easilywhite skin who burns easily

Sun Protection Factor (SPF)Sun Protection Factor (SPF)The Sun Protection Factor (SPF) is a measure of The Sun Protection Factor (SPF) is a measure of how much protection a particular sun cream how much protection a particular sun cream offers... How much longer you can stay in the sun offers... How much longer you can stay in the sun without a risk of burningwithout a risk of burning

Safe time in sun with cream = SPF xSafe time in sun with cream = SPF x time given by sun time given by sun indexindex

SPF Worked exampleSPF Worked exampleIf the weather forecast predicts that the sun If the weather forecast predicts that the sun index will be 7 what is the longest time an index will be 7 what is the longest time an untanned white person can stay in the sun if untanned white person can stay in the sun if they correctly apply sun cream with SPF 15?they correctly apply sun cream with SPF 15?

Safe time in sun with cream = SPF xSafe time in sun with cream = SPF x time given by sun time given by sun indexindex

Safe time in sun with cream = 15 x 30 Safe time in sun with cream = 15 x 30

Safe time in sun with cream = Safe time in sun with cream = 450 mins450 mins