Light - 01 - Reflection - Intro | Lecture Note

University:
High School
Course:
High School Physics
Academic year:

2024
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10
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Optics (Quantum Ch 1 to 5) 6.0 Intro to Light (ch1) Light:  Is a form of energy (radiant) that is detected by our eyes (rods & cones in retina)  Materials which emit light are luminous ◼  Ex. Light bulbs, burning match, sun Most objects are non-luminous & don’t emit light ◼ Ex. Desks, people, moon Types of Light Sources: 1. Incandescent ◼ ◼ 2. Materials that emit light when heated Ex. Filament of a light bulb Chemiluminescent/Bioluminescent ◼ ◼ Materials that produce & emit light energy by a chemical reaction which produces little heat Ex. Fireflies (bio), Glow sticks (chem) Types of Light Sources: 3. Fluorescent ◼ ◼ 4. Materials that emit light by absorbing highenergy radiation Ex. Fluorescent lightbulb - Hg vapor in bulb radiates UV, absorbed by fluorescent coating and re-radiates light. Phosphorescent ◼ ◼ Materials that “glow in the dark” Re-emission happens over longer timescales Waves:   Waves are traveling disturbances that carry energy from one point to another Transverse waves occur when the disturbance is perpendicular to the direction of the wave Wave Disturbance  Light is a electromagnetic transverse wave ◼ Speed of light = c = 3.00 x 108 m/s  period x (s) (m)   ): Wavelength ( ◼  Period (T): ◼  Time required for the wave to complete a cycle Frequency ( f ): ◼ ◼  Distance between two points of a wave separated by a complete cycle Number of cycles completed per second Inversely proportional to wavelength Formulas: f = 1/T v=fλ= λ/T Electromagnetic Spectrum: Propagation of Light: A wavefront is a line that connects all the points touched by the wave at the same time  A wave ray is an arrow that is perpendicular to the wavefront   Light rays are wave rays & describe the propagation of light & explain optic phenomena  Light travels in straight lines ◼ (linear propagation) A light ray is the path taken by light energy  A beam of light is a stream of light rays   ◼ May be parallel, converging, or diverging ◼ If light source far away, then rays parallel A ray diagram uses straight lines with arrows to show the paths of rays of light Homework: Using your text:  P28 #5  P35 #1, 2, 6, 7, 8 