waves and light and colour Theory

Waves and Light Production

Waves

  • A wave is defined as a disturbance that transfers energy without transferring matter.

    • Crest: The highest point of a wave.

    • Trough: The lowest point of a wave.

    • Amplitude: The height of the wave from the rest position; larger amplitudes carry more energy.

    • The characteristics of waves include:

    • Wavelength: The distance from one point in a wave to the next similar point, symbolized by the Greek letter lambda ((\lambda)), and measured in meters (m).

      • Energy relationship: Longer wavelengths correspond to less energy; shorter wavelengths correspond to more energy.

    • Frequency: The rate at which waves repeat, measured in cycles per second or hertz (Hz). Higher frequency results in shorter wavelengths.

      • Formula: The speed of a wave can be calculated using the equation (v = f \cdot \lambda), where (v) is speed, (f) is frequency, and (\lambda) is wavelength.

Electromagnetic Spectrum

  • The electromagnetic spectrum consists of all types of electromagnetic waves arranged by wavelength and frequency.

    • Components include:

    • Gamma rays (shortest wavelength, highest frequency)

    • X-rays

    • Ultraviolet rays

    • Visible light (Wavelength: 400 nm to 700 nm, includes ROYGBIV: Red, Orange, Yellow, Green, Blue, Indigo, Violet)

    • Infrared rays

    • Microwaves

    • Radio waves (longest wavelength, lowest frequency)

    • White light exposure: When white light passes through a prism, it refracts into a spectrum of visible light, illustrating how different wavelengths correspond to different colors.

    • Violet (400) nm, Indigo (425) nm, Blue (470) nm, Green (550) nm, Yellow (600) nm, Orange (630) nm, Red (665) nm.

Light Production

  • Light can be produced through various phenomena:

    • Incandescence: Light produced as a result of high temperatures.

    • Examples: Light bulbs, stove tops, fireworks.

    • Electric Discharge: Light produced by passing electricity through a gas.

    • Examples: Neon lights, lightning, Aurora Borealis.

    • Fluorescence: Occurs when a substance absorbs UV light and re-emits it, as seen in fluorescent bulbs.

    • Example: Fluorescent light bulbs formulated with mercury vapor and phosphor coating.

    • Phosphorescence: Similar to fluorescence but emits light slowly after the UV source is removed.

    • Example: Glow-in-the-dark materials.

    • Chemiluminescence: Light created through chemical reactions, with minimal heat produced.

    • Example: Glow sticks.

    • Bioluminescence: Naturally produced light from living organisms due to chemical reactions.

    • Examples: Fireflies, jellyfish.

    • Triboluminescence: Light generated from friction through actions like scratching or crushing certain materials.

    • Examples: Cutting a diamond, biting wintergreen lifesavers.

Additive and Subtractive Colour Theory

Additive Colour Theory

  • White light is composed of the primary colors of light: Red, Green, and Blue (RGB).

    • Combining varying amounts of these primary colors can create other colors.

    • When light striking an object is absorbed or reflected, our perception of the object's color is determined by the reflected wavelengths.

    • E.g., if a shirt absorbs blue light and reflects red and green, it will appear yellow because red + green = yellow.

    • The relationship can be represented mathematically:

    • (B = R + G + Y)

    • If a cyan light (B + G) strikes a shirt absorbing blue light, the shirt appears green because we subtract the blue:

      • (C - B = G)

Subtractive Colour Theory

  • When working with pigments (printing), the primary subtractive colors are Cyan, Magenta, and Yellow (CMY).

    • The colors seen depend on the wavelengths absorbed by the pigments. Absorbed wavelengths create the shades perceived, while reflected wavelengths produce color visuals for our eyes.

    • Similar to additive processes, subtractive color mixing can be characterized as follows:

    • The effectiveness of color perception relies on the subtractive absorption of light wavelengths by colored materials.

    • Primary subtractive colors are opposite to additive colors:

    • Primary Subtractive: Cyan, Magenta, Yellow.

    • Secondary Subtractive: Red, Green, Blue.

Conclusion

  • The light's behavior changes according to the interaction with different surfaces and media, influencing our observation of color and brightness in various contexts. Understanding these principles lays the groundwork for applications in digital media, art, and optical phenomena.