Waves: Visible Light

Waves: Visible Light

Nature of Visible Light

  • Visible light is a type of electromagnetic wave which is detectable by the human eye.
  • It forms a small portion of the electromagnetic spectrum and is located between ultraviolet (UV) and infrared (IR) waves.
  • The frequency of visible light waves is typically in the range of approximately 430-790 THz and the wavelength falls into the range of about 400-700 nanometres (nm).

Behaviour of Visible Light

  • Visible light, like all electromagnetic waves, can be reflected, refracted, and absorbed.
  • Reflection of light allows us to see objects. As per the law of reflection, the angle of incidence equals the angle of reflection.
  • Refraction is the bending of light as it passes from one medium to another. This concept is used in lenses.
  • Absorption of light is when a substance absorbs certain wavelengths of light. This phenomenon is seen when objects appear coloured: they’ve absorbed all colours but reflected the one we see.

Colours of Visible Light and Dispersion

  • Visible light can be split into different colours, this is known as dispersion. When sunlight passes through a prism, it disperses into its constituent colours.
  • The colours produced when light is dispersed range from red to violet; red light has the longest wavelength and violet light has the shortest.
  • White light is a combination of all the colours of light.

Practical Uses of Visible Light

  • In addition to enabling sight, visible light has numerous applications including in photography, film, illumination, signal processing and data transmission.
  • Lasers (Light Amplification by Stimulated Emission of Radiation) are a practical application of visible light. They produce narrow, intense beams of light and can be used in surgery, communication systems, and optical storage devices (such as CDs and DVDs).
  • Fibre-optic cables use visible light to transmit data over long distances, and are used in telecommunication and internet services.


  • Light boxes can be used to investigate reflection and refraction of light, and to understand how different coloured filters work.
  • Spectrometers are used to observe the spectral lines of different elements by separating the emitted light into a frequency spectrum. This helps in identifying the composition of a light source.
  • You can use a prism to demonstrate the dispersion of white light or investigate the properties and behaviour of lenses.