1. P2 part II

2. Use the carbon cycle to explain... 1.Why, for thousands of years, the amount of carbon dioxide in the Earth’s atmosphere was approximately constant (3 marks) Why, during the past two hundred years, the amount of carbon dioxide in the atmosphere has been steadily rising (3 marks)

3. This question is about global warming and ozone. Many people get confused between ‘the greenhouse effect’ and ‘holes in the ozone layer’. Explain the difference between the two and the scientific processes involved in each. The quality of written communication will be assessed in your answer to this question.

4. incoming solar radiation is absorbed by the Earth  Earth re-emits infrared radiation  reflected radiation is lower frequency/longer wavelength than the radiation (from the Sun) absorbed by the Earth  carbon dioxide absorbs infrared radiation  greenhouse effect describes this effect  water and methane are also greenhouse gases  increased greenhouse effect is producing global warming Holes in ozone layer  ozone layer absorbs ultraviolet radiation  chemical changes in ozone result  these changes are reversible so [O3] is usually constant  extra loss of ozone results in ‘holes’ accept ‘lower frequency radiation emitted by Earth’ for i-r

5. Climate change Hard to show on a large scale as the climate changes depending on the time of year and part of the world you are in Proven by computer models that link increased temperature with human activity Computer climate model consists of lots of equations that you can input data into and they will calculate the effect of that change in data E.g. Look at changes in direction of ocean currents and relate to temperatures on the surface of the ocean. Climate models have shown that the changes in CO 2 levels. Temperature and climate change are not due to natural changes that are occurring on the Earth

6. Impact of global warming It will impossible to continue growing some food crops in particular regions because of climate change (too dry/wet) More extreme weather events are expected, due to increased convection (wind) and larger amounts of water vapour in the hotter atmosphere Flooding of low lying land due to rising sea levels, caused by melting continental ice and expansion of water in the oceans (water expands as oceans get warmer)

7. EM waves and communication EM waves can transmit information: Infra-red – remote control, night vision Microwave – mobile phone, and satellite TV Radio – TV and radio on earth Some radio waves and microwaves are not strongly absorbed by the atmosphere (long wavelength) so can be used to carry information for radio and TV programmes Can carry information over long distances Micro waves aren’t as long and can pass through the atmosphere, so are good to use for satellite communication Optical fibres work by light waves bouncing off the inside of glass cables. Reflection allows the light to travel along bends and travel long distances Light and infrared radiation can be used to carry information along optical fibres because the radiation travels large distances through glass without it being significantly absorbed

8. Analogue and digital signals Information (photo’s/sound) travels as electrical signals Can be superimposed onto carrier EM waves Travels as either an analogue (continuous) or digital (pulsing) signal

9. Analogue and digital signals Analogue and digital signals are used to transmit information, usually through electric signals. In both these technologies, the information, such as any audio or video, is transformed into electric signals. The difference between analogue and digital technologies is that in analogue technology, information is translated into electric pulses of varying amplitude. In digital technology, translation of information is into binary format (zero or one) where each bit is representative of two distinct amplitudes.

10. Analogue and digital signals Analogue signal varies continuously Digital signal is either off or on, also known as 0 or 1 Digital receiver decodes digital signal Digital signals are an approximation of analogue signals Both signals weaken as they travel and need to be amplified They also can pick up interference (“noise”) from other electrical signals

11. Signals and noise Digital signals can be cleaned to reduce the interference and have a better quality Analogue signals cannot be cleaned up and so the signal isn’t clear Can send several signals at once along one cable

12. Signals and interference Both signals are amplified but with digital signals they are easier to clean up The noise also gets amplified with an analogue signal The amount of information used to store a digital sound/image is measured in Bytes (B) Generally the more information stored, the higher the quality of the sound or image Digital signals can also be used easier by computers as these are digital devices

13. Why is digital better? Digital has just two states On and off/0 and 1 Can recognise these even if there is interference Therefore it is easy to remove noise/clean signal Analogue signals have many different values So it is hard to distinguish between the noise and the original signal So the noise cannot be completely removed When the signal is amplified any noise is amplified

14. The diagrams show an analogue and digital signal which have been distorted by noise Explain why digital signals can be recovered after the addition of noise and why this is a benefit compared with analogue signals

15. Risk Everything we do carries a certain risk of accident or harm. Nothing is risk free. New technologies and processes based on scientific advances often introduce new risks. There may be unknown risks from a new technology e.g. Nanotechnology Make sure you can give a way of reducing a risk

16. Risk We can sometimes assess the size of a risk by measuring its chance of occurring in a large sample, over a given period of time. To make a decision about a particular risk, we need to take account both of the chance of it happening and the consequences if it did.

17. Risk To make a decision about a course of action, we need to take account of both its risks and benefits, to the different individuals or groups involved.

18. Risk People are generally more willing to accept the risk associated with something they choose to do than something that is imposed, and to accept risks that have short-lived effects rather than long-lasting ones. People would complain about living near a nuclear power station, but will be willing to use a sunbed/smoke!!

19. Risk People’s perception of the size of a particular risk may be different from the statistically estimated risk. People tend to over-estimate the risk of unfamiliar things (like flying as compared with cycling), and of things whose effect is invisible or long-term (like ionising radiation).

20. Risk You may need to distinguish between perceived and calculated risk, when discussing personal choices Suggest reasons for given examples of differences between perceived and measured risk. What you think the risk is, compared to what the calculated risk actually is

21. Risk Governments and public bodies may have to assess what level of risk is acceptable in a particular situation. This decision may be controversial, especially if those most at risk are not those who benefit. Building a new nuclear power plant in Sheffield would provide thousands of homes in England with an electricity supply that wouldn’t harm the atmosphere Who would be most at risk from this plant? Would they benefit from the plant? Would people receiving the electricity be at the same risk as those you have mentioned?

22. Risk and benefit You must be able to distinguish between the benefits of something, compared to the risks e.g. What are the benefits and risks of running the London marathon? Benefits – good for health, personal achievement, raise money for charity Risks – damage part of body during run, risk of death

23. Why do people smoke cigarettes, even though there is a well documented health risk? Benefits: look good, accepted by peers, emulate famous people who smoke Risks: health risks, lung cancer, heart disease Risks outweigh benefits..but risks don’t show for years Not everyone will get disease from smoking