Context:
Colour profoundly shapes contemporary human life by enriching the aesthetic and symbolic aspects of our surroundings, embracing cultural diversity in its interpretation, and deepening our comprehension of the world and our role within it.
Relevance:
Facts for Prelims
Dimensions of the Article:
- Understanding Colour
- What are LEDs?
Understanding Colour
What is Colour?
Colour is a form of information that our eyes interpret based on electromagnetic radiation. Objects themselves don’t inherently possess colour; instead, they appear coloured because they absorb, reflect, and/or scatter certain frequencies of visible light, which our brains then perceive as specific colours.
How Do Humans Perceive Colours?
- The human eye contains rod and cone cells that receive light information.
- Rod cells are responsible for detecting brightness.
- Cone cells are responsible for detecting wavelengths, which the brain interprets as colour.
- Humans have three types of cone cells, each sensitive to different wavelengths of light, allowing for trichromatic vision.
- The presence of three types of cone cells is why humans are referred to as trichromats.
- Birds and reptiles often have four types of cone cells, making them tetrachromats.
- Human vision is limited to wavelengths from 400 nm to 700 nm (visible light), while some insects, like honeybees and mosquitoes, can perceive ultraviolet and infrared light, respectively.
Science of Colours:
- Traditional Colour Theory: Until the late 19th century, this theory focused on how dyes, pigments, and inks could be mixed to create other colours using three primary colours (red, yellow, and blue).
- Modern Colour Theory: Modern science rejects the notion of three fixed primary colours. Instead, it focuses on the gamut of colours that can be produced by combining any three colours in different ways. Each combination creates a specific colour space, but no colour space can encompass the full range of colours visible to the human eye.
Rendering of Colours:
- Additive Colouring: This method involves mixing light of different wavelengths to create various colours. The RGB colour space (red, green, blue) is a common example, where these three colours are combined in varying intensities to produce other colours.
- Subtractive Colouring: This method creates colours by subtracting certain wavelengths from white light using dyes, pigments, or inks. For example, when a cloth is dyed, the dye absorbs specific wavelengths of light, leaving the remaining wavelengths to render the perceived colour.
Properties of Colour:
- Hue: Defined as the degree to which a colour can be described as similar to or different from standard colours like red, orange, yellow, green, blue, and violet. Complementary colours combine to produce a grayscale colour.
- Brightness: Related to an object’s luminance, which is the power emitted per unit area weighted by wavelength. The perceived brightness is how the eye interprets this power.
- Lightness: Refers to how light or dark a colour appears compared to a well-lit white object.
- Chromaticity: The quality of a colour regardless of its brightness, focusing on its purity and intensity.
What are LEDs?
- A light-emitting diode (LED) is a semiconductor device that emits light when an electric current passes through it. Light is produced when electrons and holes combine within the semiconductor material.
What are Blue LEDs?
- Blue LED light is emitted within the visible light spectrum at wavelengths between 400 to 500 nm, situated between violet and green on the spectrum.
- Blue LEDs have an active region with InGaN quantum wells sandwiched between GaN cladding layers. Adjusting the In/Ga ratio in the quantum wells can theoretically change the light emission from violet to amber.
-Source: The Hindu
