These technical briefs focus on low cost approaches to accessing clean water and sanitation. This is vital to health and well being and low costs are particularly important to poorer communities in the developing world.

Technical briefs are documents produced by Practical Action which are freely available to...

Practical Action helps local communities in the developing world gain access to services such as water and sanitation, vital for a decent quality of life. Some examples of how they go about doing this and the technologies involved are demonstrated in these videos:

• Dying for a drink - solar powered...

This resource is part of a collection of Nuffield Maths resources exploring Algebra. The demand is roughly equivalent to that in GCE A level.

Here, students use linear and quadratic functions to model water flow data and calculate percentage errors.

Water for the World was developed jointly by Engineers Without Borders UK (EWB) and Arup, a global firm of engineering consultants and specialists. There are three resources, investigating issues of water scarcity, sourcing and supply and showing how engineers can help to solve problems. Although initially designed...

This Catalyst article describes how the salty water in the oceans has some consequences for how the ocean water mixes – or does not mix. There are distinct bodies of water in the oceans which mix only very slowly. The experiments detailed in the article will explain why this is.

The article is from Catalyst...

A Catalyst article looking at renewable energy. To tackle climate change and all the challenges imposed by the need to find alternative and reliable energy sources, there is one major resource that has remained untapped until now: wave power. This article describes the size of this resource and presents the leading...

Comparing two sine waves of different amplitudes, this video shows that the intensity of a wave is proportional to the square of the amplitude.  The intensity is given I = ^P/_A, i.e., power per cross-sectional area.

This video summarises the properties of waves, i.e., reflection, refraction, diffraction and polarisation using a free App called Ripple free by Paul Falstad.  The App is very effective and versatile. 

This video uses a jelly baby wave machine to introduce the motional properties of progressive and standing waves and to introduce key terminology.

A displacement – distance graph is used to define wavelength (λ) and the phase of a wave.  A complete wave cycle is 360⁰ and from this the position of a particle...

This video explains the observations when two coherent light waves interact to form fringes.  A diagram is used to show that

λ = ^(ax)/_d, where a = slit separation and D = the distance between the slit and the projection screen, and x = distance between fringes. From these measurements...

This video introduces explains the difference between the phase difference of a wave (measured in degrees) and the path difference of a wave (measured in metres of fraction of a wavelength). 

When waves are coherent and have a path difference that is a multiple of λ, then the interference is constructive. ...

This video begins by asking the question, “why do we see rainbow colours on the surface of a DVD?”.

Light from a laser is shone through a diffraction grating to demonstrate a diffraction pattern.  The terms 0^th, 1^st and 2^nd order maxima are introduced and explained using the...

This video recaps on the idea that light sent along an optical fibre requires total internal reflection for it to progress along its length. It explains that information is sent as a series of on – off signals.  However, if light rays take different paths they can be modally dispersed, and this can degrade the...

This video models refraction using a vehicle travelling from a concrete surface to a grass surface and shows how the forward wheel slows and so the vehicle changes direction.

A diagram is then constructed to develop Snell’s law, i.e., the angle of incidence (from air) is proportional to the angle of...

This video explains how two waves passing through each other interact through the process of superposition.

The resultant interference of waves at phase differences of 0⁰ or 360⁰ is constructive, they are additive.  Whereas phase differences of 180⁰ produce destructive interference, i.e., they cancel each...