A photograph is the image of a pattern of light recorded on film. The word photography means writing or drawing with light. Without light there could be no vision or photography because it is light reflected from the world around us that makes things visible to both our eyes and the eye of the camera.
Light is a form of electromagnetic radiant energy to which the eye is sensitive. It travels at tremendous speed from its source, such as the sun, a fluorescent lamp, an electronic flash, or whatever source is used.
Light determines not only brightness and darkness, but also tone, mood and the atmosphere. Therefore it is necessary to control and manipulate light correctly in order to get the best texture, vibrancy of colour and luminosity on your subjects. By distributing shadow and highlights accurately, you can create stylized professional looking photographs.
In physics, light refers to electromagnetic radiation. The light we normally talk about in everyday life refers to the visible spectrum (the part of the electromagnetic spectrum that the human eye can see).
Other animals can see parts of the spectrum that humans can’t. For example, a large number of insects can see ultraviolet (UV) light. UV light can be used to show things the human eye can’t see, coming in handy for forensic scientists.
Isaac Newton observed that a thin beam of sunlight hitting a glass prism on an angle creates a band of visible colors that includes red, orange, yellow, green, blue, indigo and violet. This occurred because different colors travel through glass (and other mediums) at different speeds, causing them to refract at different angles and separate from each other.
Scientists study the properties and behaviors of light in a branch of physics known as optics.
Light travels very, very fast. The speed of light in a vacuum (an area empty of matter) is around 186,000 miles per second (300,000 kilometres per second).
Light travels slower through different mediums such as glass, water and air. These mediums are given a refractive index to describe by how much they slow the movement of light. Glass has a refractive index of 1.5, meaning that lights travels through it at around 124,000 miles per second (200,000 kilometres per second). The refractive index of water is 1.3 while the refractive index of air is 1.0003, meaning that air only slightly slows down light.