The human eye is an incredible piece of evolutionary engineering. But the eye is only able to see light of certain wavelengths – and it's blind to much more light than it can see.
We humans have two types of cells in our eyes that help us perceive light: rods and cones. The cones comes in three types that allow us to detect red, green and blue light. From these three receptors our brain can interpret an incredible palette of colours.
Light is measured in wavelengths, which are the distance between the peaks or valleys of the waveform. The electromagnetic scale spans from wavelengths that are measured in nanometres to wavelengths that are, literally, longer than a football pitch.
At one end of the scale we find radio waves – yes, they are in fact a form of light. With wavelengths that can be taller than a house, radio waves can travel vast distances. Because they have low energy, they don’t really interact with the environment and don’t scatter. This means that we can use them to transmit information across continents and even out into space.
Microwaves are a big part of our daily lives. They have wavelengths around a centimetre long and many common devices use microwaves to wirelessly transmit information, including your mobile phone and Leap cards.
And of course, microwave ovens use microwave light to cook food. Microwaves cause water molecules in food to vibrate. It’s this vibration that causes the temperature of the food to rise.
Infrared is just beyond the range of what the human eye can see, and has a wavelength about the thickness of a human hair.
Technology based on infrared light has been in common use in TV remote controls since the early 1980s. But we have thousands of other applications for infrared light, from predicting weather patterns to analysing molecules. The Infrared part of the electromagnetic spectrum that is most associated with heat; almost half of the energy arriving to the Earth from the sun comes as infrared light.
This is light with wavelengths of approximately 400 nanometres to 700 nanometres. These may just be numbers to you but actually they describe every colour of the rainbow, from red to violet – all the light that our eyes are able to see.
Once we go beyond visible Light, we find ultraviolet. This light has shorter wavelengths – about the size of a single virus particle, so really, really small. It also has more energy than visible light. It's this extra energy that can cause damage to materials it interacts with, including our skin.
Dogs for instance can see colours between yellow and blue – which means that they’re red/green colorblind. Insects have eyes that allows them to see much further on the ultraviolet scale than humans. Many flowers have evolved to have ultraviolet patterns on their petals that act like runway lights for insects. We can only see these hidden patterns using special cameras.
The colour king of the animal kingdom is the mantis shrimp which has 12 different colour receptors in its eyes and can see colours that we can’t even imagine.
Even shorter wavelengths have more energy but are also more dangerous and can cause significant damage to materials they encounter. Nevertheless, we have daily applications for them in the fields of medicine, security and, of course, science. The ability of X-rays to pass through soft materials, but not denser objects, is what allows us to produce shadow images of the human skeletal system.
While conducting another experiment he observed a new form of light that could pass through soft materials. He came up with the name X-ray as a temporary name, an X often being used in mathematics and science to describe something unknown. The name stuck.
Finally, we come to gamma rays: rays of light far beyond what our eyes can sense. They have a great deal of energy, so much, in fact, that they cause a great deal of damage to human cells when they come in contact with them, destroying strands of DNA. Gamma rays are produced in some nuclear processes. Their production is rare on Earth but common in outer space.