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).

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.

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.

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.