Light is a form of energy that travels in straight lines through space. We see when light bounces off objects into our eyes. Light is the fastest thing in the universe: it travels at almost 300,000 km per second (about 670 million mph), fast enough to circle the Earth 7 times in 1 second. The study of light is called optics. It explains how mirrors reflect, how lenses focus, how rainbows form and how eyes, cameras and telescopes work.
- Speed of light299,792,458 m/sThe cosmic speed limit
- Visible coloursRed to violetRoughly 400-700 nm wavelength
- ReflectionBouncing off a surfaceEqual angle in, equal angle out
- RefractionBending through a mediumLight slows down in glass and water
- From the Sun8 minutesHow long sunlight takes to reach Earth
- WavelengthDecides the colourShort = blue, long = red
What you will learn here
- What is light: the basics of how it travels and behaves.
- The visible spectrum: the colours of the rainbow.
- Reflection: light bouncing off surfaces.
- Refraction: light bending as it changes medium.
- Mirrors: flat and curved, and the images they form.
- Lenses: how they focus and magnify.
- Rainbows: the science behind the colours.
- The speed of light: the fastest speed in the universe.
Why optics matters
Almost every visual technology relies on optics. Glasses and contact lenses use refraction to focus light on your retina. Cameras use lenses to capture sharp images. Microscopes let us see bacteria; telescopes let us see distant galaxies. Lasers cut metal and read information from DVDs. Fibre-optic cables carry the internet by sending pulses of light through hair-thin glass strands. Even your phone screen, which makes light pixel by pixel, depends on the physics of how we see.