1 / 48

Physics Light & Geometric Optics

Physics Light & Geometric Optics. In this unit : A. Sources of light B. Properties of light C. Reflection of light D. Refraction of light E. Lenses and optical devices F. Vision and how our eyes work ! G. Co lo ur Th eo ry. What is light?.

leiko
Download Presentation

Physics Light & Geometric Optics

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Physics Light & Geometric Optics In this unit: A. Sources of light B. Properties of light C. Reflection of light D. Refraction of light E. Lenses and optical devices F. Vision and how our eyes work! G. ColourTheory

  2. What is light? • A form of energy that is visible (that our human eyes are capable of sensing)

  3. Sources of Light What’s the difference between light coming from the Sun or a flashlight and light coming from the Moonor a tree? The Sun producesits own light The moon / tree reflects light

  4. ...or in other words..... A luminous object is one that produces its own light. A non-luminous object is one that does not produce its own light!

  5. We see non-luminous objects because they reflect light into our eyes: Homework

  6. Rays of light Shadows are places where light is “blocked”: Shadows

  7. Types of Light Emissions • Natural – the Sun, Lightning, Forest fires..... • Artificial – I-pods and light bulbs • Materials that give off light must first absorb some sort of energy. Atoms are “excited” and immediately release the energy. Often this energy is in the form of light. • Sometimes light is related toHEAT

  8. LIGHT FROM THE SUN • The sun has "burned" for more than 4.5 billion years • It is huge ball of gas, mostly hydrogen and helium

  9. LIGHT FROM THE SUN • Hydrogen atoms combine to form helium in a “fusion” reaction, which releases lots of energy • Energy reaches Earth as light/heat, that we call sunshine

  10. Sources of Light Incandescence • Light is given off a material because it is very hot. • Not very efficient: most of the energy given off is heat and not light (95% heat, 5% light) • Examples: hot burner on a stove, incandescent bulb, lit match, gas lantern

  11. Electric Discharge Lights • Produced by an electric currentpassing through a gas (atoms get “excited” and release energy in the form of light) HEAT is produced • Different gases produce different colours Examples of electric discharge: • lightning, neon sign Examples of gases: • neon  red light; • helium  gold-light • argon  pale purple/blue light • sodium  yellow (streetlights)

  12. The gas inside the tube produces the light.

  13. Fluorescence • occurs when an object absorbs UVraysand immediately releases the energy as visible light. Examples: • highlighters contain fluorescent dyes • some detergents contain fluorescent dyes to make clothes look brighter • forensic scientists use UV lightsto detect bodily fluids • UV light used to detect counterfeit money • Ultra-whitepaper

  14. Fluorescent dye only seen under UV light Fingerprint seen under UV light

  15. Fluorescent Lights • Electricity causes mercury gas inside the light bulb to emit UV rays. • The UV light hits phosphor coating on inner surface of tube which causes visible light to be emitted. • More efficient than incandescent lights (20% light, 80% heat) and last 5-10X longer

  16. UV

  17. Light-Emitting Diode (LED) • An electronic device that allows an electric current to flow in only one direction. • No filament • Little heat produced • Very energy efficient

  18. Luminescence • Luminiscence: light is generated without the production of heat • Several types

  19. Phosphorescence • Light is produced after the absorption of ultraviolet rays and the energy is stored • Visible light is emitted over an extended period of time (minutes/hours) • Phosphorescent materials are also known as “glow in the dark”

  20. Chemiluminescence • is the emission of light with no emission of heat as the result of a chemical reaction.

  21. Triboluminescence • light caused by friction as a result of scratching, crushing, or rubbing certain crystals

  22. Bioluminescence • production of light by living organisms • the result of a chemical reaction with little or no heat produced. It is most common in marine animals.

  23. Fireflies

  24. Not stars! Glow worms on the ceiling of a dark cave

  25. Some jellyfish

  26. Many types of sea creatures!

  27. Yes there is such a thing! Anglerfish

  28. Some algae and bacteria….even some mushrooms!

  29. Bioluminescing algae

  30. Textbook Ref: Ch. 10, Section 10.1 • Page 403-408

More Related