Physics 1H

Physics 1H

1. Waves

   • Shock waves from earthquakes can be detected by seismometers and recorded on a seismograph
   • Shockwaves from earthquakes can cause damage to buildings and the Earth’s surface and tsunamis
   • P waves are longitudinal and P waves travel through both solids and liquids
   • S waves are transverse and S waves only travel through solids
   • P waves travel faster than S waves

2. The Sun

   • Exposure to UV radiation can cause: suntan, sunburn; skin cancer, cataracts and premature skin aging
   • Sunscreens can reduce damage to skin
   • SPF stands for Sun protection factor
   • Darker skins have lower cancer risk as they absorb more ultraviolet radiation so less UV reaches the underlying tissues
   • The ozone layer protects the Earth from ultraviolet radiation. Scientists were surprised to find the ozone hole. The ozone layer has been depleted by environmental pollution from CFCs

3. Key Processes

   • The higher the factor of the sunscreen, the longer the amount of time they can spend in the sun without burning. A higher factor of sunscreen means that there is less of a chance of being burnt and your skin being damaged by ultra-violet light waves
   • The ozone layer is the part of the upper atmosphere where ozone is found in the highest concentrations. The ozone there absorbs ultraviolet radiation, preventing most of it from reaching the ground. This is important because ultraviolet radiation can lead to skin cancer. Near the end of the last century, scientists discovered that ozone levels over the Antarctic were reduced. This discovery was unexpected. Chemists knew that reactive chlorine atoms could destroy ozone. They also knew that chemicals called chlorofluorocarbons - CFCs - break down in ultraviolet light to release reactive chlorine atoms. Scientists used these ideas to explain the low ozone levels. CFCs were once used widely in insulating foam and aerosol spray-cans. Once released, they gradually spread through the atmosphere, eventually reaching the ozone layer. Once there, they destroy ozone. CFCs have now been almost completely replaced by chemicals that do not cause this damage