Have You Ever Wondered How Our Eyes Perceive The Various Colours? | CENTRE FOR FOUNDATION STUDIES IN SCIENCE OF UNIVERSITI PUTRA MALAYSIA

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Have you ever wondered how our eyes perceive the various colours?

Most humans are estimated to perceive approximately one million distinct colours. This ability arises from the functions of three types of cone cells in a healthy human eye, each capable of detecting around 100 different colour shades. As a result, one million possible colour combinations can be seen by humans.

The issue is, how do we see colour?

1. The source of light and the colour of the object that is being see

To see the object, we need light. We cannot see in the dark. Light is the only type of electromagnetic wave that is visible to our eye. Sun, light bulbs and electronic displays can produce light. The wavelength of light visible to humans ranges from 400 nm (nanometers) to 700 nm, which covers violet, indigo, blue, green, yellow, orange, and red. Therefore, to see the object, we need source of light and the object. When light hits an object, some of the light is absorbed while some is reflected. For example, when we perceive yellow, our eyes detect a combination of reflected red and green light. A yellow object reflects both of these wavelengths, and the perception of yellow is created.

2. The reflected light enters the eyes

This process begins when light passes through the cornea and the lens. The cornea is the transparent outer layer that helps focus the light. Next, the lens adjusts the light directly to the retina.

3. The eyes process colours

The retina contains two types of photoreceptor cells: rod cells and cone cells. Rod cells help us see in dim light (only black-and-white vision). Meanwhile, cone cells can detect colours, since it active in bright light. There are three types of cone cells, which correspond to different wavelengths of light: S-cones (short wavelength), M-cones (medium wavelength), and L-cones (long wavelength). The blue light is detected by S-cones, whereas green light is recognized by M-cones. L-cones are sentitive to red light. Therefore, the reflected yellow light activates M-cones and L-cones. These cones will send yellow signal to the brain.

4. The brain creates the colour image

The brain analyzes the signals from the rods and cones, and then sends the signals to the visual cortex to form the yellow image (if M-cones and L-cones are activated).

Summary

The human eye perceives colours by detecting specific wavelengths of light using three types of cone cells in the retina. The brain processes and combines signals from these cells, allowing us to perceive a various spectrum of colours around us.

"Figure 1: Photoreceptor cell. By www.scientificanimations.com. Retrieved from Wikipedia, https://commons.wikimedia.org/wiki/File:Photoreceptor_cell.jpg. Licence under Creative Commons Attribution-Share Alike 4.0 International license.”