NATS 1870 Understanding Colour Study Guide PDF

Study Guide for NATS 1870: Understanding Colour Lesson 1: Introduction to the Course Overview of the Course Map: ○ This course examines colour from multiple disciplines, including: History of Colour Systems: Learn how ancient and modern societies classified...

Study Guide for NATS 1870: Understanding Colour Lesson 1: Introduction to the Course Overview of the Course Map: ○ This course examines colour from multiple disciplines, including: History of Colour Systems: Learn how ancient and modern societies classified and studied colour. Physics of Light and Colour: Understand the properties of light, including its wave-particle duality and interaction with matter. Human Vision and Colour Perception: Explore how the eye and brain work together to perceive colour. Chemistry of Dyes and Pigments: Investigate the creation, properties, and use of colour substances in art and industry. Artistic Usage of Colour: Study colour theory, contrasts, and applications in design. Example: Imagine painting a picture. Understanding how light works, why your eyes see colours, and how to mix paints for the best results combines science and art. Lesson 2: History of Light and Colour – Part 1 Ancient Greeks: ○ Anaxagoras: Proposed that light consists of particles emitted by luminous objects. Suggested the moon reflects sunlight. Example: Think of the moon as a mirror reflecting sunlight. Just like a flashlight beam reflects off a shiny surface. ○ Democritus: Believed that colour perception arises from atomic shapes and arrangements. Example: Imagine tiny Lego blocks of different shapes creating different colours in your mind. ○ Plato: Linked colours to the four classical elements: fire, water, air, and earth. Believed sight resulted from rays emitted by the eyes. Example: Picture looking at a fire and seeing red or staring at water to see a calming blue. ○ Aristotle: Proposed colour arises from the mixing of light and darkness, observing colours in the sky and natural phenomena. Example: Think about sunsets blending light (orange and yellow) with the darkness of night. ○ Euclid: Applied geometry to study light, laying groundwork for future optical studies. Example: Imagine using a ruler to measure how light bounces off a mirror at an angle. Middle Ages: ○ Al-Kindi: Developed ideas on how light propagates and refracts through different media.  Example: Like how a straw looks bent in a glass of water because the light bends. ○ Alhazen (Ibn al-Haytham): Revolutionized optics in his "Book of Optics," emphasizing experiments and explaining vision as light entering the eye. Example: Think about how a camera lens lets light in to form a picture, just like your eye does. ○ Robert Grosseteste: Investigated light’s symbolic and scientific properties, emphasizing its importance in understanding the natural world. Example: Imagine seeing a rainbow and wondering why light splits into so many colours. ○ Albertus Magnus: Examined light and colour’s connection to the divine and physical sciences. Renaissance: ○ Johannes Kepler: Studied how light forms images in the eye and its relationship to celestial bodies. Example: Like tracing the path of sunlight through a magnifying glass to focus it. ○ Willebrord Snell: Formulated Snell’s Law, describing how light bends when entering different media. Example: Like aiming a flashlight at water and noticing how the beam bends. ○ Leonardo da Vinci: Studied light and shadow extensively, contributing to artistic realism and scientific understanding. Example: Think of a drawing where shadows make a face look three-dimensional. Separation of Colours in Light and Materials: ○ Isaac Newton: Demonstrated that white light is composed of various colours using a prism. He identified the spectral colours (red, orange, yellow, green, blue, indigo, violet). Example: Shine a flashlight through a glass prism to see a rainbow on the other side. ○ James Harris: Built on Newton’s work, contributing theories about colour perception. ○ Johann Heinrich Lambert: Developed mathematical models to describe light intensity and reflection, foundational for photometry. Lesson 3: History of Light and Colour – Part 2 Physiology of Human Perception: ○ Thomas Young: Proposed the trichromatic theory, stating the eye has three types of colour receptors sensitive to red, green, and blue light. Example: Think of mixing red, green, and blue lights to make all the colours on your TV screen. ○ Johann Wolfgang von Goethe: Focused on the psychological and emotional effects of colour, contrasting with Newton’s physical approach. Example: Red might feel exciting, while blue feels calm.  ○ James Clerk Maxwell: Applied mathematical principles to additive colour mixing and pioneered early colour photography. Example: Imagine blending red and green light to make yellow. ○ Ewald Hering: Introduced the opponent-process theory, suggesting colour perception involves opposing pairs like red-green and blue-yellow. Example: Think of how your eyes might see green dots after staring at a red object for too long. ○ Albert H. Munsell: Created a systematic way to classify colours using hue, value (lightness), and chroma (intensity). Example: Like organizing crayons into neat rows of shades and brightness. ○ Johannes Itten: Defined colour contrasts and relationships, influencing modern art and design theory. Example: Complementary colours like blue and orange make each other stand out. Modern Colour Systems: ○ Munsell Colour System: A standardized system for specifying colours based on their properties. ○ CMY Model: A subtractive colour model used in printing, combining cyan, magenta, and yellow. Example: Think about how your printer mixes cyan and yellow to make green. ○ RGB Model: An additive colour model used in screens, combining red, green, and blue to produce colours. Example: A smartphone screen uses tiny red, green, and blue lights to make white or any other colour. ○ CIE 1931: Defined a colour space to standardize human colour perception. ○ CIE LAB: Created a more perceptually uniform colour space for applications like colour matching. ○ Photoshop: Software enabling precise digital colour manipulation and design. Example: Like adjusting the brightness or hue of a photo to make it more vibrant. Lesson 4: Defining Light as Electromagnetic Energy Defining Light: ○ Light is electromagnetic radiation detectable by the human eye, with wavelengths ranging from 400 to 700 nanometres. Example: Imagine light as a wave traveling like ripples in a pond but much, much faster. Electromagnetic Spectrum: ○ Includes gamma rays, X-rays, ultraviolet, visible light, infrared, microwaves, and radio waves. Visible light occupies only a small portion. Example: A rainbow shows only the "visible" part of the spectrum.  Wave Properties of Light: ○ Light behaves as a wave, with properties such as: Wavelength (λ): Determines colour (shorter wavelengths are blue; longer are red). Frequency (ν): Number of wave cycles per second, inversely proportional to wavelength. Example: Think of a spring stretched and compressed—shorter stretches represent higher frequencies. Particle Properties of Light: ○ Light also behaves as particles (photons), with energy proportional to frequency. Example: Imagine photons as tiny balls of energy bouncing off a surface. Lesson 5: Light and Matter Structure of Atoms: ○ Bohr Model: Describes electrons orbiting the nucleus in quantized energy levels. Example: Picture planets orbiting the sun in fixed paths, but they can jump to different orbits. ○ Absorption and Emission: Occur when electrons move between energy levels, releasing or absorbing photons. Example: Like stepping up or down stairs and gaining or losing energy with each step. Interaction of Light and Matter: ○ Absorption: Light energy is absorbed by matter, often raising electrons to higher energy states. Example: A black T-shirt absorbs sunlight and feels warm. ○ Reflection: Light bounces off surfaces. Example: Looking into a mirror and seeing your reflection. ○ Transmission: Light passes through a material. Example: Light passing through a glass window. ○ Scattering: Light is deflected in various directions by particles. Example: The sky looks blue because sunlight scatters off air molecules. Temperature and Light: ○ Hotter objects emit shorter wavelengths (blue light), while cooler objects emit longer wavelengths (red light). Example: A stove burner glows red when hot but turns blue when extremely hot. Lesson 6: Decoding Starlight Blackbody Radiation: ○ Objects emit light based on temperature. The peak wavelength (λmax) shifts with temperature (e.g., hotter stars appear bluer).  Example: Compare a red-hot metal rod to a white-hot one; the hotter one glows brighter and whiter. Spectra: ○ Continuous Spectra: Emitted by dense objects like stars. Example: Like light emitted from a glowing light bulb. ○ Absorption Spectra: Dark lines where light is absorbed by cooler gas. Example: Like shining light through colored glass and seeing parts of the spectrum missing. ○ Emission Spectra: Bright lines from excited gases emitting light. Example: Neon signs glow in bright colors because of emission spectra. Colours of Stars: ○ Depend on temperature and composition, analyzed through spectra. Spectral Analysis: ○ Determines properties like temperature, chemical composition, and movement of stars. Lesson 6: Decoding Starlight (Continued) Kirchhoff’s Laws: 1. Continuous Spectrum: A solid, liquid, or dense gas emits light at all wavelengths. Example 1: A heated metal rod glows with a range of colours that blend together seamlessly. Example 2: The filament of an incandescent bulb emits a smooth, continuous spectrum. 2. Emission Spectrum: A hot, low-density gas emits light at specific wavelengths (bright lines). Example 1: Neon lights emit bright red, orange, or yellow lines depending on the gas. Example 2: Hydrogen gas emits bright pink and purple lines in its emission spectrum. 3. Absorption Spectrum: A cooler gas in front of a continuous spectrum source absorbs specific wavelengths, creating dark lines. Example 1: Sunlight passing through Earth's atmosphere shows dark lines due to oxygen absorption. Example 2: A rainbow viewed through a filter with certain chemicals shows gaps where light is absorbed. Lesson 7: History of Stellar Spectroscopy Fraunhofer’s Spectral Lines: ○ Fraunhofer identified dark lines in the Sun's spectrum, marking the birth of stellar spectroscopy. Example 1: These lines are like a barcode revealing the Sun's chemical composition.  Example 2: Observing a star's absorption lines can identify elements like hydrogen or helium. The Legacy of Women in Stellar Spectroscopy: ○ Women like Annie Jump Cannon classified stars by their spectra, while Cecilia Payne-Gaposchkin discovered stars are mostly hydrogen. Example 1: Cannon's classification system (OBAFGKM) organizes stars by temperature, from blue-hot to red-cool. Example 2: Payne’s discovery explains why the Sun emits hydrogen’s signature lines. Lesson 8: The Ray Model of Light Ray Model of Light: ○ Describes light as traveling in straight lines called rays, useful for explaining reflection and refraction. Example 1: A flashlight beam creates a straight path visible in fog or dust. Example 2: Shadows form when objects block light rays traveling straight. Absorption, Transmission, Dispersion, Refraction: ○ Absorption: Light absorbed by an object and converted to heat. Example 1: A black car heats up more in sunlight than a white car. Example 2: Blackout curtains block light by absorbing it. ○ Transmission: Light passes through an object. Example 1: Glass windows let sunlight into a room. Example 2: A clear water bottle lets you see inside. ○ Dispersion: Light separates into colours based on wavelength. Example 1: A prism creates a rainbow by bending light differently for each colour. Example 2: Rain droplets scatter sunlight into a rainbow. ○ Refraction: Light bends as it enters a medium with a different density. Example 1: A pencil looks bent when half-submerged in water. Example 2: A straw in a glass of water appears to shift at the surface. Reflection and Scattering: ○ Reflection: Light bounces off a surface. Example 1: A mirror reflects your image. Example 2: A shiny car hood reflects sunlight. ○ Scattering: Light deflects in many directions when it hits small particles. Example 1: The sky is blue because short wavelengths of sunlight scatter more than long wavelengths. Example 2: Sunset colours (orange and red) occur because long wavelengths scatter less, reaching your eyes directly. Lesson 9: Refraction of Light  Index of Refraction: ○ Measures how much light slows down and bends in a medium. Example 1: Glass has a higher index than air, bending light significantly. Example 2: Diamonds sparkle due to their high refractive index. Snell’s Law: ○ Describes the relationship between angles of incidence and refraction based on refractive indices of two media. Example 1: Light entering water at an angle bends toward the normal line. Example 2: Glass lenses bend light to focus it, following Snell’s law. Total Internal Reflection: ○ Occurs when light hits a boundary at an angle greater than the critical angle and reflects entirely. Example 1: Fiber optic cables use total internal reflection to transmit light signals. Example 2: A diamond sparkles when light reflects internally before exiting. Lesson 10: Diffraction of Light Diffraction in Waves: ○ Light bends around obstacles or through narrow openings. Example 1: Ripples spread after passing through a gap in a barrier in water. Example 2: Light forms fringes when it passes through a small slit. Interference Patterns: ○ Light waves overlap, creating bright and dark bands due to constructive and destructive interference. Example 1: Soap bubbles show rainbow colours due to thin-film interference. Example 2: CDs reflect colourful patterns when tilted under light. Thin Film Interference: ○ Occurs when light reflects from the top and bottom surfaces of a thin layer. Example 1: Oil spills on water create iridescent colours. Example 2: Soap bubbles shimmer with rainbow-like colours. Diffraction Gratings: ○ Surface structures split light into spectra. Example 1: CDs show rainbows because the grooves act as diffraction gratings. Example 2: The Morpho butterfly’s wings create iridescent blue due to diffraction. Lesson 11: Photography – Part 1: From Telescopes to Digital Cameras Telescopes: ○ Use lenses and mirrors to collect and magnify light from distant objects. Example 1: Galileo’s telescope allowed humans to see Jupiter’s moons. Example 2: The Hubble Space Telescope captures detailed images of galaxies.  CCD Imagers: ○ Convert light into electronic signals for digital imaging. Example 1: Cameras on phones use CCDs to take pictures. Example 2: Astronomers use CCDs to capture starlight for analysis. Digital Cameras: ○ Capture images by converting light into digital data. Example 1: A DSLR camera uses a sensor to take high-quality photos. Example 2: Security cameras use digital imaging for surveillance. Lesson 12: Colours in the Sky Aurora (Northern/Southern Lights): ○ Caused by charged particles from the sun interacting with Earth’s magnetic field and atmosphere. Example 1: Green auroras occur when oxygen atoms are excited by solar particles. Example 2: Purple auroras result from nitrogen molecules. Rainbows: ○ Formed by refraction, reflection, and dispersion of sunlight in raindrops. Example 1: A double rainbow appears when light reflects twice inside raindrops. Example 2: The colours appear in the same order (ROYGBIV) because red bends the least and violet bends the most.