2. Light and Sound In this unit: 1)Properties of light 2)Reflection 3)Colors 4)Refraction

3. Photons Light energy comes in tiny bundles called photons. Lowest energy photons-dull red color Highest energy photons-deep violet color

4. Part 1 – Properties of Light Light travels in straight lines: Laser

5. Light ray Narrow beam of light that travels in a straight line.

6. Light travels VERY FAST – around 3.0 x 10 8 metres per second. (186,282.397 miles per second) At this speed it can go around the world 8 times in one second.

7. Light travels much faster than sound. For example: 1)Thunder and lightning start at the same time, but we will see the lightning first. 2) When a starting pistol is fired we see the smoke first and then hear the bang.

8. We see things because they reflect light into our eyes: Homework

9. Reflection Occurs when light bounces off a surface.

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

11. Properties of Light summary 1)Light travels in straight lines 2)Light travels much faster than sound 3)We see things because they reflect light into our eyes 4)Shadows are formed when light is blocked by an object

12. Part 2 - Reflection Reflection from a mirror: Incident ray Normal Reflected ray Angle of incidence Angle of reflection Mirror

13. The Law of Reflection Angle of incidence = Angle of reflection In other words, light gets reflected from a surface at ____ _____ angle it hits it. The same !!!

14. Color Each different color of light has a different wavelength.

15. Color White light is not a single color; it is made up of a mixture of the seven colors of the rainbow. We can demonstrate this by splitting white light with a prism: This is how rainbows are formed: sunlight is “split up” by raindrops.

16. The colors of the rainbow: Red Orange Yellow Green Blue Indigo Violet

17. Adding colors White light can be split up to make separate colors. These colors can be added together again. The primary colors of light are red, blue and green: Adding blue and red makes magenta (purple) Adding blue and green makes cyan (light blue) Adding all three makes white again Adding red and green makes yellow

18. Seeing color The colour an object appears depends on the colors of light it reflects. For example, a red book only reflects red light: White light Only red light is reflected

19. A white hat would reflect all seven colours: A pair of purple trousers would reflect purple light (and red and blue, as purple is made up of red and blue): Purple light White light

20. Our eyes cannot see the colors of visible light that are absorbed by an object. When an object absorbs all light waves, it appears to be black. We see black

21. Refraction Occurs when light bends when crossing a surface or moving through a material. Light changes speed and bends.

24. medium Material a wave travels through

25. transparent Light can pass through Objects on the other side can be seen clearly Example: Glass

26. translucent Some light can pass through. -Objects on the other side can be seen, but not clearly. -Example: Stone glass panel

27. opaque No light can pass through Example: A door