Skip main navigation

What is light?

Light and the electromagnetic spectrum is a topic often taught at upper secondary level. Here's a short video to help explain what light is.

Light, in all its forms, is the astronomer’s tool for understanding our Universe and the objects we find in it. Although we can only see a small portion of the full electromagnetic spectrum with our eyes, we have built telescopes and detectors that enable us to study our Universe at every wavelength of light.

But what is light and what are its properties? We answer these questions in our aptly titled video – “What is light?”. You can use this video in the classroom and pause it at various points to reiterate specific concepts in class.

Here are the main science points mentioned in the video:

  • Light is an electromagnetic (EM) wave.
  • Electromagnetic waves can be produced by the oscillation of an electron.
  • Light has a wavelength, a frequency and a speed.
  • It is the fastest thing in the Universe – in a vacuum it travels at a mind-blowing 300,000,000 metres per second!
  • The electromagnetic spectrum is the entire range of electromagnetic waves.
  • Each part of the EM spectrum has a different wavelength of light.
  • Gamma-rays have the shortest wavelengths and the most energy, while radio waves have the longest wavelengths and the least energy.
  • Light can interact with matter through processes like scattering, reflection and absorption.
  • Objects that might not be observable in visible light can often be observed by switching to a different wavelength, such as infrared.
  • The expansion of our Universe causes light from galaxies to be stretched to longer wavelengths. This is known as redshift.
  • We can’t directly observe black holes as they don’t emit any detectable type of light.

You can download the ‘Colour and wavelengths in space’ resource below to use with this video in your classroom.

This article is from the free online

Physics, Astronomy, and Space: Teaching Secondary Science

Created by
FutureLearn - Learning For Life

Reach your personal and professional goals

Unlock access to hundreds of expert online courses and degrees from top universities and educators to gain accredited qualifications and professional CV-building certificates.

Join over 18 million learners to launch, switch or build upon your career, all at your own pace, across a wide range of topic areas.

Start Learning now