Light and Reflection PDF

1. Definitions (Sources of Light, EM Spectrum, and Light Types) Sources of Light ​ 1.​ Luminous: Objects that emit their own light (e.g., the Sun, a light bulb). ​ 2.​ Non-luminous: Objects that do not emit light but reflect light from luminous sources (e.g., the Moon). Types...

1. Definitions (Sources of Light, EM Spectrum, and Light Types) Sources of Light ​ 1.​ Luminous: Objects that emit their own light (e.g., the Sun, a light bulb). ​ 2.​ Non-luminous: Objects that do not emit light but reflect light from luminous sources (e.g., the Moon). Types of Light Production ​ ​ Incandescence: Light produced by heating an object to a high temperature (e.g., filament in a light bulb). ​ ​ Electric Discharge: Light produced when electricity passes through a gas (e.g., neon lights, lightning). ​ ​ Phosphorescence: Light emitted slowly over time after absorbing UV light (e.g., glow-in-the-dark stickers). ​ ​ Fluorescence: Immediate light emission when a material absorbs UV light (e.g., fluorescent lamps). ​ ​ Chemiluminescence: Light produced by a chemical reaction without heat (e.g., glow sticks). ​ ​ Triboluminescence: Light produced by friction or scratching/crushing crystals (e.g., sugar being crushed). ​ ​ Bioluminescence: Light produced by living organisms through chemical reactions (e.g., fireflies, jellyfish). ​ ​ Light-Emitting Diodes (LEDs): Efficient light produced by the movement of electrons in a semiconductor. Properties of Light ​ 1.​ Light travels in straight lines. ​ 2.​ Light can reflect, refract, and bend. ​ 3.​ Light is a form of electromagnetic radiation. ​ 4.​ Light travels at 300,000 km/s in a vacuum. Electromagnetic Spectrum ​ ​ Order (longest to shortest wavelength): Radio waves → Microwaves → Infrared → Visible light → Ultraviolet → X-rays → Gamma rays. ​ ​ Visible Spectrum: ROYGBIV (Red, Orange, Yellow, Green, Blue, Indigo, Violet). The Human Eye ​ ​ Parts to Know: ​ 1.​ Cornea: Focuses light entering the eye. ​ 2.​ Lens: Fine-tunes focus by refracting light. ​ 3.​ Retina: Detects light and converts it to signals for the brain. ​ 4.​ Pupil: Controls the amount of light entering the eye. ​ 5.​ Optic Nerve: Sends signals from the retina to the brain. 2. Refraction and Calculations Refraction ​ ​ Definition: The bending of light as it passes from one medium to another due to a change in speed. ​ ​ Light bends toward the normal: When entering a denser medium (e.g., air to glass). ​ ​ Light bends away from the normal: When entering a less dense medium (e.g., glass to air). Key Formulas 1.​ n= c/v Index of Refraction (n): Where: ​ ​ n = index of refraction ​ ​ c = speed of light in a vacuum (3.00S x 10^8 m/s) ​ ​ v = speed of light in the medium ​ 2.​ Snell’s Law: sin Oi /sin Or ​ Refraction Triangle (for quick calculations): Index of refraction = speed of light in vacuum(c)/ Speed of light in Medium (v) How Light Bends in Different Mediums ​ 1.​ Air to Glass: Slows down, bends toward the normal. ​ 2.​ Glass to Air: Speeds up, bends away from the normal. ​ 3.​ Water to Glass: Slows down slightly, bends toward the normal. Air to Acrylic: Light slows down and bends toward the normal because acrylic is denser than air. Air to Oil: Light slows down and bends toward the normal, but slightly less than in acrylic because oil is less dense than acrylic. 3. Reflection and Mirror Labeling Types of Reflection ​ 1.​ Specular Reflection: Light reflects off a smooth surface in one direction (e.g., mirror). ​ 2.​ Diffuse Reflection: Light reflects off a rough surface in many directions (e.g., paper). Mirror Diagrams ​ 1.​ Concave Mirror (converging): ​ ​ Reflects light to a focal point. ​ ​ Uses: Telescopes, makeup mirrors. ​ ​ Ray Diagram Rules: ​ ​ A ray parallel to the principal axis reflects through the focal point. ​ ​ A ray passing through the focal point reflects parallel to the axis. ​ 2.​ Convex Mirror (diverging): ​ ​ Spreads light outward. ​ ​ Uses: Security mirrors, car side mirrors. ​ ​ Ray Diagram Rules: ​ ​ A ray parallel to the principal axis reflects as if it’s coming from the focal point behind the mirror. 4. Lenses and Image Labeling Types of Lenses ​ 1.​ Convex Lens (converging): ​ ​ Focuses light to a point. ​ ​ Uses: Magnifying glasses, cameras, human eyes. ​ ​ Ray Diagram Rules: ​ ​ A ray parallel to the principal axis refracts through the focal point. ​ ​ A ray through the center of the lens passes straight without bending. ​ 2.​ Concave Lens (diverging): ​ ​ Spreads light outward. ​ ​ Uses: Glasses for nearsightedness, peepholes. ​ ​ Ray Diagram Rules: ​ ​ A ray parallel to the principal axis refracts outward as if it’s coming from the focal point. ​ ​ A ray through the center of the lens passes straight without bending. 5. Important Tips for the Quest ​ 1.​ Memorize the definitions of light production and properties. ​ 2.​ Practice calculating refraction problems using the formulas. ​ 3.​ Be able to explain how light bends when moving between different mediums. ​ 4.​ Draw and label concave/convex mirrors and lenses accurately. ​ 5.​ Review ray diagrams for reflection and refraction thoroughly.