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What is Light?

What is Light?. Baby don’t hurt me, no more. Speed of Light. The speed of light is 3.0 x 10 8 m/s or 300 000 km/s. Speed = distance/time or . Example. Calculate the time it takes for light to travel from London to Calgary if the distance is 3213km. c = 300 000 km/s t = d/c = 3213 km

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What is Light?

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  1. What is Light? Baby don’t hurt me, no more.

  2. Speed of Light • The speed of light is 3.0 x 108m/s or 300 000 km/s. • Speed = distance/time or

  3. Example • Calculate the time it takes for light to travel from London to Calgary if the distance is 3213km. c = 300 000 km/s t = d/c = 3213 km 300 000 km/s = 0.0171 s

  4. Example • How long would it take for light to travel from the Sun to the Earth (d = 149,600,000 km)? • How long would it take (in days) a space shuttle to cover this distance if it went at a speed of 28,003 km/h?

  5. Sources of Light

  6. Incandescence • The production of light from an object that is at a very high temperature.

  7. Electric Discharge • The process of producing light by passing an electric current through air or a gas. • Lightning is an example • Different gases produce different colours • Neon is red orange • Argon is violet to lavender blue • Nitrogen is more pink

  8. Phosphorescence • a process in which energy absorbed by a substance is released relatively slowly in the form of light. • Generally UV light which is absorbed • Glow in the dark stickers

  9. Fluorescence • Occurs when an object absorbs UV light and immediately releases the energy as visible light. • CFL light bulbs • Rocks/minerals

  10. Chemiluminescence • Release of light and heat due to a chemical reaction. • Glow sticks!

  11. Bioluminescence • Chemiluminescence in living organisms • Jellyfish and the firefly!! • Firefly’s glow due to chemical reaction of oxygen and the enzyme luciferase

  12. Triboluminescence • light generated when material is pulled apart, ripped, scratched, crushed, or rubbed (friction) through the breaking of chemical bonds in the material. • Lifesavers in the dark – does it make a spark!? • Peeling two pieces of duct tape apart

  13. Light Emitting Diode (LED) • a material emits light after passing an electric current through it. • Christmas lights – doesn’t emit heat, doesn’t require a filament, more energy efficient.

  14. “Laser” • Laser Video • Light Amplified by Stimulated Emission of Radiation • Electromagnetic waves emitted exactly the same (direction and energy) • Pure in colour, very intense and concentrated into one narrow beam.

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