5.2 The energy of electromagnetic waves The energy density of an electric field E is Although we will not prove it in this unit, a very similar result applies to magnetic fields. The energy density of a magnetic field B is 5.1.3 Getting agreement with Faraday's law Substituting Equation 7.21 into Faraday's law gives This shows that a propagating electric wave is automatically accompanied by a transverse magnetic wave. The magnetic field oscillates in the y-direction, which is perpendicular to the direction of propagation and 4.6 Postscript to Section 4 This section has considered a small number of chemical pollutants of water and has examined what is known about their harmful effects on animals, humans and the environment. You should be aware of a number of important general points that arise from what you have read. First, there is an enormous variety of chemical pollutants; you have read about only a few. Secondly, the evidence that chemical pollutants are potentially harmful is often more convincing from studies of animals than it is fro 4.3 Mercury Mercury is a naturally occurring metal which, in its pure form, is not particularly toxic. Under normal conditions of temperature and pressure, it is a silvery-white liquid which readily transforms into a vapour. When vaporised, it enters the atmosphere, remains there for a long time, and is circulated globally (WHO, 2005b). Through chemical reaction and precipitation it enters freshwater lakes and rivers, where it accumulates in the sediments at the bottom. Here it is transformed by bacteria 3.6.2 Exponential increase: bacteria Bacteria are single-celled organisms. Many different types of bacteria exist and they populate almost every environment on earth, from deep oceans to soil to human intestines. Several bacteria are beneficial to us: for instance, our gut bacteria can help to break down foodstuffs that we would otherwise find difficult to digest. However, some bacteria produce harmful toxins and if they grow in an uncontrolled way in our bodies this can have serious health consequences. If a bacterium is 3.6.1 Radioactivity and bugs! Many natural processes involve repeated doublings or halving at regular intervals. You may have come across this already in your work, in the context of bacterial growth or radioactivity. In this section, we are going to look in more detail at bacterial growth and radioactivity and we will be using graphs to examine how the numbers of bacteria or numbers of radioactive atoms change over time. 2.2.2 Precision Measuring the same sample should give the same result every time if the equipment is precise. In practice, the information displayed by a measuring device can depend on several factors (such as temperature and humidity) and can drift slightly over time. Nevertheless, during the time it takes to complete a measurement sequence, all measurements ought to remain within a specified, small margin of error, often marked on the equipment. We will see later on, in Author(s): 1.11 Addition and subtraction in practice – fluid balance A common healthcare example that uses addition and subtraction involves calculating the fluid balance of a patient. Fluid balance is a simple but very useful way to estimate whether a patient is either becoming dehydrated or overfilled with liquids. It is calculated, on a daily basis, by adding up the total volume of liquid that has gone into their body (drinks, oral liquid medicines, intravenous drips, transfusions), then adding up the total volume of liquid that has come out of their 1.5 Rounding to decimal places Sometimes the result of a calculation gives a number with lots of decimal places – far more than you need or could reliably measure. For instance, suppose a patient is required to receive 5 ml of medicine a day, evenly spaced in three injections. How much medicine should they be given in each dose? To divide the 5 ml of medicine into three equal parts would mean measuring out 5 ÷ 3 = 1.6666 ml (where the 6s keep repeating, or recurring indefinitely). It's not realistic or feas Introduction This sample of S110 material is taken from Module 2, entitled Using numbers and handling data. As you read the material, bear in mind that it is taken from a work-based course, designed for those who are employed in the health services, perhaps as a paramedic or as operating theatre staff. If you were a student on the course, you would have an OU tutor to help you, plus a work-based mentor supplied by the employer – normally the NHS. The aim is to use the workplace as a teaching aren 5.2 Precambrian and Lower Palaeozoic Basement The Precambrian and Lower Palaeozoic Basement of the British Isles is a series of nine discrete, exotic terranes whose boundaries are fault systems that have undergone large but usually unknown amounts of lateral and vertical movement over time (Figure 11 and Author(s): 3.7 Moon39: Apollo 14 station C The panorama was collected by Alan Shepard at station C-Prime. (QuickTime, 500KB, note: this may take some time to download depending on your connection speed) 3.4 Moon36: Apollo 12 station 2 Pete Conrad took this pan early in EVA-1 from a position due west of the Lunar Module. Al Bean can be seen in several frames taking documentation photos of the Solar Wind Collector (SWC) that he has just deployed. (QuickTime, 500KB, note: this may take some time to download depending on your connection speed) 2.3 Missions to the Moon David A. Rothery Teach Yourself Planets, Chapter 6, pp. 66–75, Hodder Education, 2000, 2003. Copyright © David Rothery The Moon was the first extraterrestrial target for space missions. Probes have been directed towards it since almost the very dawn of the space age (see below), and it was the main focus of the 1960s–1970s ‘space race’ between the USA and the then Soviet Union. In the end, only NASA attempted to put people on the Moon, and the six suc 3 What are compounds? Click on the video clip to watch Elements and Compounds, which focuses on water and its constituent elements. Click below to v 9.3.1 Weber's Law Pioneering work on the relationship between ΔI and S was done by the German physiologist, Ernst Weber in the 1830s. Weber found that the increment in stimulation required for a JND was proportional to the size of the stimulus. Weber had subjects lift a small ‘standard’ weight (S) and then lift a slightly heavier ‘comparison’ (T) weight and judge which was heavier. He found that when the difference between the standard and comparison weights was small, the subjects found 9.3 Differential sensitivity Absolute thresholds represent only one type of threshold; one could also ask whether the subject can detect a difference between two stimuli. The threshold for detection of difference is called a difference threshold or difference limen (DL). The difference threshold is a measure of the smallest detectable difference between two stimuli. Basically it answers the psychophysical question: ‘How different must two stimuli (e.g. two weights, two colours, two sounds) b 2.1.1 Science and regularity ‘Our experience shows that only a small part of the physical Universe needs to be studied in order to elucidate its underlying themes and patterns of behaviour. At root this is what it means for there to exist laws of Nature, and it is why they are invaluable to us. They may allow an understanding of the whole Universe to be built up from the study of small selected parts of it.” John D. Barrow (1988), The Worl 6 Summary There are two areas of general concern regarding the introduction of GM crops and food: the possible impacts on human health and on the environment. For some critics of GM technology, this reflects a feeling that GM technology is unnatural, as compared to conventional crop breeding. However, many techniques used in conventional crop development, for example, intergeneric and interspecific crossing, haploid breeding and mutation breeding, are highly technological and seem very far from being n 3.2 Integration of anatomy and behaviour with biochemical and physiological strategies in evaders We know from Section 2.3 that small desert rodents remain cool by staying in their burrows for all or part of the day. Kangaroo rats (Dipodomys spp.; see Figure 20 in Section 2.3) depend on metabolic water as there is little or no water available in their diet of seeds. Kangaroo rats appear to be ill-adapted for
Activity 1: Elements and compounds
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