Light is often a symbol of greatness, and rightly so, with its ability to be both visible and invisible. It exists in the form of wavelengths, which we view as a multitude of colours. However, the powers of light extend beyond that: light has the potential to manipulate the way we see things, resulting in mesmerising and sometimes mind-boggling illusions.

 

Colour is nothing without light 

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Light is a form of electromagnetic radiation that lies on a spectrum. Due to our limited ability to see these electromagnetic waves, we are only able to see what is characterised as visible light [1]. Colours exist as different wavelengths in a rainbow-coloured order, with red being the longest wavelength and violet being the shortest wavelength, and these colours are detected by cone-shaped cells in our eyes [2]. There are two types of common light rays outside of our visible light range, ultraviolet and infrared light, positioning animals who can detect these to have superior vision [3]. Moreover, as colours and lights exist in the form of wavelengths, temperature can affect what is seen. For example, hot objects radiate short wavelengths, changing the colour we see, such as a hot flame having a range of red to blue colours, because of the way heat radiates from it [1].

 

Role of light in the mirage 

 

There is an age-old question: what would you do with the power to be invisible for a day? Well, the ability to do this is not that far into the future, with many scientists developing methods to make this a reality. Magicians use a common trick of placing mirrors strategically for a disappearing act. The use of mirrors reflects light away from the object so all we see is empty space because our eyes are programmed to view light as a straight line, so we struggle to process it any other way [4]. So far, this has worked successfully to disappear objects  on a small scale. However, scientists are finding ways to amplify this technique to disguise larger items or even a person. 

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A recent viral TikTok video is baffling people as to how a mirror can reflect an object hidden behind a piece of paper. Let’s unpack the science behind this trick. When light rays hit an object, photons of light are reflected off it in all directions, and some of these rays will hit the mirror. So, when you look at the object at a certain angle, you can also see it being reflected into the mirror, despite having a boundary in-between [5].

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Similarly, this sort of illusion can be seen in nature itself. There is an optical phenomenon in the desert, which produces a mirage image on the ground. Because heat affects wavelengths of light, a warm surface on the ground can bend the rays of light from the sun upward, creating what is known as an inferior image. For example, this could make it seem like there is water on the ground, when in fact it is a reflection of the sky because an image of a distant object can be seen below the actual position of the object. Likewise, if there was cool air underneath, it would create a superior image [6]. This is all due to a temperature gradient created between the ground and the atmosphere above it [7].

 

Invisibility in the movies 

 

Violet from The Incredibles and the Fantastic Four heroine, the Invisible Woman, can both become invisible at their own will. While these examples are only in the movies, there is some truth here. Light can be manipulated to create an illusion, although it is unlikely to appear as realistic as an invisibility cloak. A more theoretically possible form of light manipulation would be the advanced technology portrayed in movies such as Marvel and Harry Potter. It features hovercrafts and a flying car, respectively, that possess the ability to camouflage themselves against their background. This is done through reflective plates, which become a mirror to match the surrounding objects and reflect light away to conceal the object.

 

Another example of a cinematic light-based mirage is in the movie Now You See Me, which includes a series of magic tricks. In one scene, a character is shown to stop rain mid-air and control its movement with his hands. Sorry to ruin the magical illusion, but this one is merely a simple trick of strobe lights flashing repeatedly at the right frequency which makes it seem like the rain is stopped in mid-air. It also requires some movie magic and a large-scale rain machine to control the droplets [8].

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There has been so much progress on movie-making to make creative imaginations a reality. For example, there is a new focus on transformation optics, the application of metamaterials to manipulate electromagnetic radiation. Metamaterials are designed with unique patterns to interact with light and other energy forms artificially. For example, Pyrex glass and oil have the same refractive index, so if you put these items together, the refraction of light against these objects can make it disappear out of view [9]. This is an easy trick you can try at home. 

 

Overall, light has a multitude of abilities that are still untapped. However, there is hope in society's ability to take advantage of technology and discover more uses for light, and its ability to evade the human eye. We could soon be having magic shows worthy of contending with even the most bizarre movies.