Light

1. Light

2. Light • All light is produced by excited atoms

3. Excited Atoms • Electrons in an energy level have a specific amount of energy • If an electron absorbs energy, it is bumped into a higher energy level • This produces an unstable or excited atom

4. Photons • Atoms do not like to be excited. • The electron will loose the extra energy by giving off a photon, allowing it to fall back into its original energy level • Light is produced • Photon – a packet of energy released by an excited electron

5. Electromagnetic Spectrum An arrangement of all electromagnetic waves by decreasing wavelength and therefore increasing frequency

6. The Visible Spectrum Longest wavelength ROY – G – BIVshortest wavelength Red Orange Yellow Green Blue Indigo Violet

7. Light behaves like a wave The wave theory of light explains most of the properties and behavior of light very well. However, it can no longer explain all the things we’ve observed about light. Light behaves like a particle High energy light will produce an electric current when it strikes a metal plate, while low energy will not. If light was a continuous wave, even the energy from the lowly “red” light would eventually be absorbed and cause some electron movement – this does not happen. Behavior of Light

8. Light Strikes Matter…. 3 Things Can Happen: • Light can be transmitted • Light can be absorbed • Light can be reflected

9. Light Can Be Transmitted Light passes through the substance it strikes • Transparent– light passes through so you can see clearly – like window • Translucent– Light passes through but it is scattered so you cannot see clearly – like wax paper • Opaque – Light does not pass through – like construction paper

10. Light Can Be Absorbed Light passes through a substance and stays there Example: When light hits a red stop sign, the stop sign reflects mostly red wavelengths and absorbsall other colors so we do not see them

11. Light Can Be Reflected Light strikes a substance and bounces back Example: When light hits a red stop sign, the stop sign reflects mostly red wavelengths and absorbs all other colors so we do not see them

12. Reflection Reflection –bouncing back of a wave when it hits a surface it can’t pass through • Regular Reflection – very little scattering; the image looks exactly like the object • Diffuse Reflection – light is scattered in many different directions; if image is formed at all, it does not look like the object

13. Mirrors • Mirrors REFLECT light • Types of mirrors • Plane – a flat surface • Concave – surface of mirror curves inward • Convex – surface of the mirror caves outward

14. Refraction Refraction – the bending of waves as they enter a different medium • Some mediums cause light to bend more than others • Prism – an object that forms a spectrum as light passes through it

15. Lenses • Lenses REFRACT light • Types of lenses • Concave – thicker at the edges than at the center • Convex – thicker at the center than at the edges

16. Optics • Optics is the science of controlling light • Light can be controlled in 3 ways: 1. Block it 2. Reflect it 3. Bend it (Mediums, mirrors, and lenses are used in optics)