The third configuration of air column that we shall consider is that enclosed by a conical tube. Figure 17 shows the normal modes of vibration for a conical tube plotted in terms of pressure. As you would expect, there is a pressure antinode at the closed tip of the cone and a pressure node at the open en
Author(s): The Open University

In the previous two sections on standing waves in cylindrical tubes, we assumed that at an open end there must be a pressure node. In fact, the pressure node (and the corresponding displacement antinode) actually lies a small distance outside the tube. The effect is that the air column behaves as though it were a little longer than it really is by an amount called the end correction. Because of this end correction, the resonance frequencies will be a little lower than originally expect
Author(s): The Open University

We'll now turn our attention to the setting up of standing waves in an air column contained within a cylindrical tube that is open at one end but closed at the other. Straight away we can say that the closed end must be a displacement node since the air molecules can't move at this boundary. That means it must be a pressure antinode. The open end, as we saw previously, will be a displacement antinode (that is, a pressure node).

Now, you may recall that the distance between a node and a
Author(s): The Open University

If standing waves are set up when two travelling waves moving in opposite directions interact, then how are standing waves set up on a string and why are they set up only at certain frequencies?

To help answer these questions, I want you first to imagine a length of string that is fixed at one end and held in someone's hand at the other. Suppose the person holding the string flicks their end of the string in such a way that an upward pulse is sent along the string.

As the pulse pa
Author(s): The Open University

Fungi (e.g. species such as Penicillium which are used for manufacture of antibiotics, and yeast) are generally unicellular non-photosynthetic organisms which can tolerate acid conditions. They are capable of degrading highly complex organic compounds. They utilise much the same food sources as bacteria but they require less nitrogen since their protein content is lower. Fungi play an important role in sewage treatment.

In polluted water, particularly near to a se
Author(s): The Open University

Protozoa are microscopic single cell animals. They utilise solid substances and bacteria as a food source. They can only function aerobically, and in a stream which contains little organic degradable matter they can become a predominant microbial type. They play an important part in sewage treatment where they remove free-swimming bacteria and help to produce a clear effluent.

In an aquatic environment, there are three main types of protozoa:

Author(s): The Open University

Bacteria are organisms of special significance to the study of clean and polluted waters because they break down organic matter. While most of them are not harmful to humans, some bacteria (e.g. Clostridium) are pathogenic. Most bacteria are retained on a filter of pore size 0.45 μm and all bacteria are trapped on a filter of 0.22 μm. They are important in sewage treatment, and in solid waste disposal. They are extremely abundant in almost all parts of the aquatic env
Author(s): The Open University

Algae are photosynthetic organisms that are generally aquatic; they are primary producers. Many freshwater algae are of microscopic size, but when amassed can be seen as a green, brown or blue-green scum. Blue-green algae are capable of producing toxins and these have caused the death of wild animals, farm livestock and domestic pets which have consumed the contaminated water. The toxins can produce a painful rash on human skin. The extract below shows what happened off the west coast
Author(s): The Open University

The main proponent of this approach to learning, David Kolb, put forward a theory which he intended to be sufficiently general to account for all forms of learning (Kolb, 1984). He argued that there are four distinctive kinds of knowledge and that each is associated with a distinctive kind of learning. The four kinds of learning are:

• concrete experiencing

• reflective observation

• abstract analysis

• activ
Author(s): The Open University

## Activity 1

A self-review exercise for your learning file

The aim of this activity is to encourage you to take a problem-solving approach to your own learning, and to be proactive. The first part asks you to refle
Author(s): The Open University

Learning how to learn has become an important goal in higher education. There is a national context in which an emphasis on ability to learn has come to prominence. It is now widely asserted that an ability to learn is as important an outcome of university study as knowledge of a discipline. This is a view put forward strongly by employers, for example, who have an interest in the employability of graduates and the skills they bring into the work place. It is a view which has been reiterated
Author(s): The Open University

Brittle fractures were discovered quickly in the mass of debris hauled from the river. Such samples became the focus of increasing effort as time went by, simply because they were unexpected. So the possible failure mechanisms were immediately narrowed down when brittle fractures of critical components started to emerge from the river.

A plan was needed to determine the chain of events leading up to and during the collapse. That sequence would necessarily depend on which parts had broken first, and a fault tree would enable a plan of action in isolating the cause (or causes) of the disaster. Such a systematic approach is known as fault-tree analysis or FTA, and is part of the armoury of methods used by accident investigators. With large-scale and devastating accidents, all possibilities, however remote, need evaluation in t
Author(s): The Open University

The Graeco-Roman city of Paestum
What can archaeological remains tell us about early cities and the people who lived in them? This album examines the important remains of one city, Poseidonia in Italy, founded towards the end of the 7th century BCE by colonists from the Greek city of Sybaris. Although only twenty-five per cent of the site has been excavated to date, much of its history and culture can be traced through its buildings, inscriptions, and decoration. After it became a colony of Rome in 273 BCE, it became known a
Author(s): The OpenLearn team

Buildings of ancient Rome
Rome: a majestic city with a rich past, spanning over two and a half thousand years. What remains to be seen of ancient Rome? As the heart of the Roman Empire, ancient Rome’s archaeological remains have been studied and admired for centuries, many being well-preserved due to their incorporation into newer structures. This album explores the sites of some of the republican temples in Rome’s Campus Martius, and relates them to the men who built them. The Roman Forum, centre of political and so
Author(s): The OpenLearn team

The Arts Past and Present: the Benin Bronzes
Are ancient sculptures ethnographic artefacts or works of art? How can objects like these throw light on the relationship of our culture to other cultures, both in the past and in the present? This album explores some of the issues surrounding interpretation and display of bronze sculptures originating in Benin in West Africa. The video explores the academic dilemmas behind decisions that Western curators have to make about how the pieces should be displayed. In the supporting audio, Open Unive
Author(s): The OpenLearn team

The Arts Past and Present: Ireland
Do we use our buildings to declare who we are? How far does our heritage influence our collective identity? This insightful album reveals Ireland's shifting attitudes towards its cultural heritage. In 1922 when it broke free of British rule to become an independent nation state, the Irish nationalists abandoned high-profile buildings like Dublin Castle as it was symbolic of their British oppressors, and it fell into ruin. Yet they proudly restored older sites like Cashel and New Grange, which i
Author(s): The OpenLearn team

There is evidence that public knowledge about social work in Scotland is ‘fairly low’, with apparent confusion between social services and welfare benefits – ‘the social’ – and over the boundaries between social work and social care. The MORI survey also reported that those most likely to be in need of social support – older people, lower social income and minority ethnic groups – were particularly ill informed about availability and access to services (Davidson and King, 2005
Author(s): The Open University

Myth in the Greek and Roman Worlds: the Temple of Diana at Nemi
How was mythology used by ancient Romans in their everyday lives? At Nemi to the south of Rome, the sanctuary of the goddess Diana provides us with a snapshot of Roman life and society. This album explores some of the fragments of objects found at the site of Diana's temple, such as a street entertainer's clay lamp, an ex-slave's votive statue and a miniature model of the Temple itself. Containing significant clues about social mobility, these cult objects reveal how lower social classes used my
Author(s): The OpenLearn team