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...

This video begins by showing a demonstration of total internal reflection (TIR) through a semi-circular glass block.

It develops an understanding of TIR by showing that as the angle of incidence (θ_i) increases so too does the angle of refraction (θ_r).  Eventually, as  θ_i is...

This video shows how interference from two sound wave sources can produce both constructive (louder sound) and destructive (softer sound) interference patterns.  A demonstration using microwaves reinforces this idea. Microwaves are generated and passed through a double slit.  The resultant interference of waves is...

Produced by the Wellcome Trust, these resources include an interactive evolutionary tree and a video of the Tree of Life. These materials will help students to find out more about the work of Charles Darwin and evolution. The resources contain:

Tree of life video: The video is a short...

This video explains how atoms are the fundamental building blocks of all matter and that they are made from sub-atomic particles (proton, neutron and electron). The simple structure of a hydrogen atom is made from plasticine. The video explains how adding a neutron to the hydrogen atom does not change its...

Much of this video shows how many people do not understand how the seasons are caused.  There is a small section at the end that attempts to clarify the cause.  

This video provides a great overview to 3D printing, looking first at different ways of manufacture, before explaining the 3D printing process. The video is...