Why does light have colours

Red light is the only light that is reflected from the shirt. If only blue light is shone onto a red shirt, the shirt would appear black, because the blue would be absorbed and there would be no red light to be reflected. White objects appear white because they reflect all colours.

Black objects absorb all colours so no light is reflected. The retina of our eyes contains two types of photoreceptors — rods and cones. The cones detect colour. The rods only let us see things in black, white and grey.

Our cones only work when the light is bright enough, but not when light is very dim. This is why things look grey and we cannot see colours at night when the light is dim.

There are three types of cones in the human eye that are sensitive to short S , medium M and long L wavelengths of light in the visible spectrum. These cones have traditionally been known as blue-sensitive, green-sensitive and red-sensitive, but as each cone is actually responsive to a range of wavelengths, the S, M and L labels are more accepted now. These three types of colour receptor allow the brain to perceive signals from the retina as different colours.

Some estimate that humans are able to distinguish about 10 million colours. The primary colours of light are red, green and blue. Mixing these colours in different proportions can make all the colours of the light we see. This is how TV and computer screens work. If you look at a screen with a magnifying glass you will be able to see that only these three colours are being used.

For example, red and green lights are used to make our brain perceive the image as yellow. When coloured lights are mixed together, it is called additive mixing. Red, green and blue are the primary colours for additive mixing. If all of these colours of light are shone onto a screen at the same time, you will see white.

Evolution led bees to adapt ultraviolet vision because flowers leave scatter ultraviolet patterns, allowing the insects to easily identify targets and pollinate. This is what spectrometers are for. Tibi is a science journalist and co-founder of ZME Science.

He writes mainly about emerging tech, physics, climate, and space. In his spare time, Tibi likes to make weird music on his computer and groom felines.

Home Other Did you know? What makes things coloured — the physics behind it Have you ever wondered where do colours come from? May 10, Reading Time: 5 mins read. This way, when light hits matter one or more of the following phenomena happens: reflection and scattering.

Most objects reflect light, but some are more reflective than others, like metals. This is directly related to the number of free electrons that are able to pass from atom to atom with ease. Instead of absorbing energy from the light, the free electrons vibrate and the light energy is sent out of the material at the same frequency as the original light coming in. The electrons thus absorb most of the incoming energy, with little or no reflection. If the incoming light energy is much lower or much higher than that required for the electrons comprising an object to vibrate, then the light source will pass through the material unchanged.

This way matter will look transparent to the human eye, such as in the case of glass. If the energy of the incoming light is the same as the vibration frequency of the electrons in the material, light is able to go deep into the material, and causes small vibrations in the electrons. The vibrations are then passed on from atom to atom, each vibrating at the same frequency as the incoming light source.

This makes the light inside the material look bent. Light is refracted when it enters the prism, and each colour is refracted by a different amount. This means that the light leaving the prism is spread out into its different colours, a process called dispersion. Here are the seven colours of the spectrum listed in order of their frequency, from the lowest frequency fewest waves per second to the highest frequency most waves per second :.

There are three primary colours in light: red, green and blue. Light in these colours can be added together to make the secondary colours magenta, cyan and yellow. All three primary colours add together make white light. The way coloured light mixes is very different from the way that paint does. When light hits a surface, some of it is absorbed and some of it is reflected. The light that is reflected is the colour of the object in that light.