Resources by Physics Online

The equation for velocity of waves on a string

The video states that the velocity (v) of a wave moving along a string is related to the strings tension (T) and its mass per unit length (μ).  The unit of tension is the Newton (N) and the unit of mass/length is kg/m.

A simple interrogation of the formula v = √(T/ μ) shows that as T increases so too does...

The wave equation

This video begins with the mnemonics Very furry lambs and Cute furry lambs.

Using a model of a railway carriage (its length, x and time taken to travel, t) the equation for velocity (v = ^x/_t) is derived.  Equating the length of the carriage to wavelength, λ and time to the period, T the...

Thermal insulation

A pair of videos that studies the thermal insulation properties of bubble wrap. This first video allows students to see an experiment that investigates how increasing the number of layers of bubble wrap around a beaker affects the cooling of hot water. The second explains how to interpret the data, plot the graph...

Transformer output

The properties of a transformer are investigated in this video, specifically how the number of turns on the coils affects the output. 

Unit prefixes

This video introduces prefixes that are used to describe the size of a measurement.  For example, the prefix m is called milli and represents 1/1000 = 0.001 = 10^-3.

The following prefixes are described:

milli (m) - 10^-3

micro (µ) - 10^-6

nano (n) - 10...

Verifying the principle of moments

This video demonstrates a simple experiment to investigate the principle of moments.

Wave amplitude and intensity

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.

Wave properties - reflection, refraction, diffraction and polarisation

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. 

Wave terminology -wavelength, period, amplitude and phase difference

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...

Waves - coherence and path difference

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. ...