Science Library - free educational site

Diffraction, resolution and polarization

Waves through a gap in a barrier

Here is a film of a rippletank with a barrier with a gap in it. What do you observe?

Single slit diffraction pattern.

An oscillation is a system in which a mass moves towards an equilibrium point. Examples of oscillations are a spring pushing and pulling a mass, a ball bobbing on water, a coin rolling up and down the inside of a curved bowl, and a skateboarder on a half-pipe.

Oscillation occurs when the force is zero at the mid-point (equilibrium), and if the mass moves away from the equilibrium point, a force increase proportionally to the distance away it is. As the spring stretches, the force pulling the object back to the mid-point increases.

All oscillations have cycles, which have a period and frequency.


A pendulum is an example of an oscillation with a period and frequency.

pendulum equipment

An oscillation is a motion which is self-replicating. It may be, as in the case of a spring, due to elastic potential converting to kinetic energy, and back again. Or it may be, as in the case of a pendulum, due to kinetic energy converting to gravitational potential, which then reconverts to kinetic.

Pendulum: can you time the period and calculate the length of the string?

The period of an oscillation is the time interval between two positions that are identical in space. This means that a period of a pendulum consists of two swings.

The frequency, λ, of a pendulum is the number of double swings (back and forth) per second, and is expressed in Hertz (Hz).

The mass and amplitude of swing has no effect on the period of a pendulum. Instead, only the length of the string will determine the period of oscillation for a any mass.

The Maths

The period T of a pendulum of length L is:

$$T = 2π √{L/g}$$

Note: the value of π/√g is 0.987, or very close to 1. Therefore, an approximation of the time it takes a pendulum to make a single swing (half a period) is simply √L.

A pendulum 1.0m long has a period of 2 secs, or 1 second a swing. This is how Galileo 'swung' the pendulum clock industry into being!

Content © All rights reserved. Created : August 31, 2014 Last updated :February 27, 2016

Latest Item on Science Library:

The most recent article is:


View this item in the topic:

Vectors and Trigonometry

and many more articles in the subject:

Subject of the Week


Environmental Science is the most important of all sciences. As the world enters a phase of climate change, unprecedented biodiversity loss, pollution and human population growth, the management of our environment is vital for our futures. Learn about Environmental Science on

Environmental Science

Great Scientists

Edwin Chadwick

1800 - 1890

Sir Edwin Chadwick was an English social reformer who was instrumental in bringing about reform in Britain, particularly with regards sanitation and public health.

Sir Edwin Chadwick
Lugano English

Quote of the day...

She looked as if she had been poured into her clothes and had forgotten to say 'when'.

ZumGuy Internet Promotions

Renewable energy media services