Red Lights: Why Red Is The Colour Of Choice For Signals And Towers Surface

Have you ever wondered why we often see red lights on top of tall towers or as signals on vehicles and buildings? Well, there's a good reason for that! It's not just a random choice. The colour red has special properties that make it useful in these situations. In this article, we're going to explore the simple science behind why red light is commonly used in signals and on top of towers. We'll break it down step by step, so everyone can understand why red is the colour of choice for these important jobs. So, let's dive into the world of red light and discover its secrets!

This Story also Contains

1. Colour Perception
2. Red Light and Wavelength
3. Scattering and Absorption

Colour Perception

Colour vision in humans is a complex process that relies on the interaction of our eyes, brain, and electromagnetic spectrum. Here's an overview of how humans see colour:

The Eye's Structure: Photoreceptors are specialised cells found in the retina of the human eye. Rods and cones are the two primary types of photoreceptor cells involved in colour perception.

Rods and Cones: Rods are responsible for low-light vision but have nothing to do with colour perception. Cones, on the other hand, are in charge of detecting and discriminating between distinct colours. There are three types of cone cells, each sensitive to a different wavelength range:

• S-cones (short-wavelength cones) are blue light-sensitive.

• Green light is sensitive to M-cones (medium-wavelength).

• Long-wavelength L-cones are sensitive to red light.

Colour Mixing: These cone cells sense light as it enters the eye. The information from these cones is then processed by the brain to produce the perception of colour. The principles of additive colour mixing are frequently used to explain colour perception:

• Longer wavelengths (620-750 nanometers) are especially responsive to red cones.

• Medium wavelengths (about 520-570 nanometers) are especially responsive to green cones.

• Shorter wavelengths (about 450-495 nanometers) are especially responsive to blue cones.

Colour Combinations: Colour vision is created by different combinations of signals from these three types of cones. Perceiving yellow, for example, requires the stimulation of both red and green cones. White light activates all three cone types in the same way.

The electromagnetic spectrum is a classification of electromagnetic radiation based on wavelength and frequency. Visible light, which humans can sense, is only a small fraction of this spectrum, with wavelengths spanning from roughly 380 to 750 nanometers. varied colours have varied wavelengths, with red having the longest and violet having the shortest.

Wavelength is important in colour perception because our three types of cone cells in the eye are sensitive to distinct wavelength ranges. S-cones are primarily stimulated by shorter wavelengths (about 380-495 nm), resulting in the impression of blue and violet. M-cones are activated by medium wavelengths (about 520-570 nm), resulting in green vision. Longer wavelengths (620-750 nm) primarily excite L-cones, resulting in the sense of red. The whole spectrum of colours we can perceive is produced by different combinations of cone cell activation driven by wavelengths.

Red Light and Wavelength

Red light has a strong place in the visible spectrum. It is one of the main colours that humans can sense and is found on the longer end of the spectrum. In colour perception, red light is easily distinguished and is frequently linked with warmth, vitality, and intensity.

Red light has a defined wavelength range, roughly between 620 and 750 nanometers. This range is longer than the wavelengths associated with colours like blue and green, which are located in the visible spectrum's shorter end. The precise range can vary slightly depending on individual perception and lighting environment.

Scattering and Absorption

Different colours of light interact with the Earth's atmosphere in distinct ways due to variations in their wavelengths. These interactions include scattering and absorption:

• Scattering: The process by which light is diverted in different directions as it interacts with particles or molecules in the atmosphere. Shorter wavelengths, such as blue and violet, scatter more readily, giving the sky its blue look.

• Absorption: Specific wavelengths of light can be absorbed by certain molecules in the atmosphere. Ozone, for example, absorbs ultraviolet (UV) light, but water vapour absorbs infrared light. These mechanisms of absorption contribute to the overall composition of daylight.

Rayleigh scattering, an important phenomenon in atmospheric optics, governs how different colours of light interact with the Earth's atmosphere. This scattering phenomenon is especially noticeable with shorter wavelengths of light, particularly blue and violet light. It happens when incoming sunlight, which contains a rainbow of colours, collides with air particles and molecules that are smaller in size than the wavelength of the light. As a result, shorter wavelengths, such as blue and violet, are heavily scattered in all directions. This scattering dominates the midday sky, giving it a distinctive blue colour. Longer wavelengths, such as red and yellow, encounter significantly less scattering, allowing them to reach our eyes more directly and contribute to the vibrant colours of sunrises and sunsets.

When travelling through the Earth's atmosphere, red light stands out for its resistance to both dispersion and absorption. This resilience is due to its longer wavelengths, which typically range between 620 and 750 nanometers. Red light experiences less dispersion in the context of Rayleigh scattering than shorter wavelengths such as blue and violet. Because of the reduced scattering, red light can maintain its colour and intensity over long distances, making it useful for long-distance signalling and visibility in a variety of environmental circumstances. Furthermore, red light absorbs little in the environment, allowing it to pass through atmospheric components with little distortion or attenuation, making it a reliable choice for applications ranging from emergency signalling to astrophysical observations.

And so, whether it's guiding ships through treacherous waters, warning aircraft of towering structures, or signalling emergencies in the dead of night, the choice of red light isn't random but a result of its remarkable properties – its resistance to scattering and absorption in the Earth's atmosphere. In the world of light and signals, red remains a steadfast and reliable companion, a beacon of safety and guidance in our ever-changing and dynamic environment.