Presentation on theme: "P1h(ii) Stable Earth You will learn about: Ultraviolet radiation and how to avoid its harmful effects The ozone layer and how it is monitored www.PhysicsGCSE.co.uk."— Presentation transcript:
P1h(ii) Stable Earth You will learn about: Ultraviolet radiation and how to avoid its harmful effects The ozone layer and how it is monitored
Suntans Tanning is caused when ultraviolet radiation from the Sun mutates the skin cells. Too much time in the Sun causes the skin to go red, burn or even blister. Your skin may even show signs of premature ageing. More sun may lead to cancer. The eyes are not safe too. Being in the sun without sunglasses can cause cataracts – the clouding of the lens in the eye causing blurred vision. People enjoy the benefits of the Sun when sunbathing. Vitamin D and a healthy glow are just two. However, too long in the Sun can have some damaging effects. Sunglasses, suntan lotion as well as covering up are easy ways to reduce the Sun’s harmful effects.
Safe Sunbathing IMPORTANT: Skin contains cells that produce melanin. An increase of ultraviolet radiation causes more melanin to be produced. Melanin absorbs ultraviolet radiation so reduces the risk of skin cancer. This is why people with darker skin are less likely to suffer with skin cancer. When you go out into the Sun it is a good idea to watch the weather forecast so you know what the Sun Index is. People with white skin need to be extra careful due to the lack of melanin. Sun Index tells you: The strength of the Sun How long you can go into the Sun before burning. This map shows the South of England as yellow which is Sun Index 3-5. There is little risk of harm from the Sun today. When you use a sunscreen the length of time you can stay safely in the Sun can be calculated by: Safe length of time to stay in the Sun wearing sunscreen = SPF number x time given in sun index Using the Equation. A Sun Index of SPF (Sun Protection Factor) 15 means you can stay in the Sun 15 times longer. If the Sun Index is 6 how long can you stay in the Sun for? Without sunscreen= 30 minutes. With sunscreen = SPF number x time given With sunscreen = 15 x 30 minutes = 7.5 hours. Sun Index Risk 1-2Low Risk 3-4Avoid Sun times more than 1-2 hours 5-6Burns in minutes 7-10Severe burns in minutes
Ozone The stratosphere is part of our atmosphere and it contains a gas called ozone. Ozone absorbs ultraviolet radiation. Between 1970 and 1985 scientists noticed a rapid drop of ozone. It caused a lot of alarm. Scientists though they had made a mistake. They even thought the satellites recording the ozone was malfunctioning too. But collaborations from scientists from around the world helped to make scientists realise the truth – the ozone layer was depleting. NASA satellites record each year the amount of ozone in the stratosphere. It is clear it is thinner in the central part of each image – this is over Australia and the South Pole. Fortunately, the ozone layer is thickening but it will take several more decades before it is repaired. We learnt previously that higher frequency (or shorter wavelength) electromagnetic waves have more energy than lower frequency waves. The short wavelength ultraviolet radiation breaks the bonds in the ozone and the energy is absorbed meaning the ultraviolet radiation does not reach Earth’s surface. This photodissociation keeps us safe. However, during the middle of the 20 th Century pollutants were discharged into the atmosphere. Chlorofluorocarbons (CFCs) from aerosols and refrigerators were largely to blame. They thin the ozone layer. This thinning is sometimes called a ‘hole’ but it isn’t really. The South Pole is the coldest place on Earth and the ozone thinning was noticed there first because the chemical destruction of ozone works better in colder conditions. The Government were quick to step in. The Montreal Protocol was signed in 1987 saying the world should cut CFCs by 50% before the year In fact the world banned all CFCs before It was a worldwide effort to protect everyone.
Questions 1.Why would you advise a young child to use a higher SPF sunscreen than yourself? 2.Cyclists spend a lot of time in the Sun. Which parts of their body should they apply extra sunscreen to? 3.Jodie wants to go out into the Sun. She watched the weather forecast and it said the Sun Index for the day was 7. How long can she stay in the Sun for without sunscreen? How long can she stay in the Sun for wearing sunscreen SPF 20? 4.Why do you think people were so worried about the depletion of the ozone layer in the 1980s?
Questions 1.Why would you advise a young child to use a higher SPF sunscreen than yourself? Their skin may not produce much melanin so they have a higher chance of getting cancer. 2.Cyclists spend a lot of time in the Sun. Which parts of their body should they apply extra sunscreen to? Anywhere exposed – arms, legs, hands, head (through cycling helmet), nose and ears. 3.Jodie wants to go out into the Sun. She watched the weather forecast and it said the Sun Index for the day was 7. How long can she stay in the Sun for without sunscreen? How long can she stay in the Sun for wearing sunscreen SPF 20? Sun Index 7 means can stay in Sun for about 30 minutes. If wearing SPF 20: 20 x 30 minutes = 10 hours. However, this is not recommended as the sunscreen could wear off due to water or friction so it would be advisable to top up as frequently as possible. 4.Why do you think people were so worried about the depletion of the ozone layer in the 1980s? The ozone would not absorb the energy from the harmful ultraviolet radiation. This means more would reach the surface of the Earth causing a higher number of people suffering from skin cancer. Sun Index Risk 1-2Low Risk 3-4Avoid Sun times more than 1-2 hours 5-6Burns in minutes 7-10Severe burns in minutes