1. Lesson 25 Any substance that a wave moves through is a medium Sound waves, Earthquake waves, and ocean waves all require matter to transfer energy 1

2. Lesson 25 Electromagnetic waves can transmit energy through a vacuum or empty space. 2

3. Lesson 25 Wave behavior is affected by the type of medium the wave interacts with or travels through 3

4. Light Waves and Media In order for you to see any object, the object must give off light. Objects give off light in only two ways a.Being luminous b.Being illuminated 4

5. Light Waves and Media Luminous objects are those that emit their own light Illuminated objects are those that can reflect light to your eyes The amount of light that is reflected from an object depends on the surface of the object. 5

6. Light Waves and Media A smooth surface reflects more light than a rough surface This occurs because a rough surface scatters reflected light in many different directions 6

7. Light Waves and Media Have you ever noticed that an asphalt driveway seems hotter on a summer day than a concrete sidewalk 7

8. Light Waves and Media This occurs because light that is not reflected from the surface of an object may be absorbed by the object and converted to thermal energy 8

9. Light Waves and Media 9 The color and surface texture of a material have an effect on whether how easily light is absorbed by the object Smooth and light colored objects reflect more light than they absorb

10. Light Waves and Media Objects with a rough texture and dark color absorb more light than they reflect A dark rough textured object will often feel hotter than a smooth, light colored object 10

11. Shape Affects Deflection When light rays reflect from a surface they do so in a predictable way that is explained by the Law of Reflection 11

12. Shape Affects Deflection The Law of Reflection states that the angle at which any wave strikes a reflecting surface is equal to the angle at which the wave is reflected from the surface 12

13. Shape Affects Deflection The angle at which a wave strikes a surface is called the angle of incidence The angle of at which a wave is reflected from a surface is called the angle of reflection 13

14. Shape Affects Deflection According to the Law of Reflection, the angle of incidence is equal to the angle of reflection The shape of a surface affects how it reflects light. 14

15. Shape Affects Deflection A plane mirror is a mirror with a flat surface Light striking a plane mirror is reflected straight back, resulting in an upright image that is the same size as the original object 15

16. Shape Affects Deflection Curved mirrors reflect at an angle, producing different kinds of images 16

17. Shape Affects Deflection A convex mirror curves outward, resulting in an image your eyes detect as upright and reduced in size * The side mirrors on cars are convex mirrors 17

18. Shape Affects Deflection A concave mirror curves inward, taking the shape of the inside of a bowl If an object is very close to the mirror, light is reflected in a way that an enlarged, upright image is produced. 18

19. Shape Affects Deflection If the object is very far way, the image is reduced in size and upside down 19

20. Transmission of Light Many materials are classified according to how well they transmit light A material that permits light to pass through is transparent 20

21. Transmission of Light Whether or not an object is transparent depends on how much and what colors of light it transmits You can see through the transparent materials Air and clear glass are examples of common transparent materials 21

22. Translucent Translucent materials transmit some light but also scatter light in all directions Frosted glass and waxed paper are translucent materials 22

23. Translucent Opaque materials allow no light to pass through wood, carpet, and ceramic plates are examples of opaque objects 23

24. Media and Wave Speed The speed at which a wave travels is called wave speed Wave speed is affected by the medium through with a wave travels Mechanical waves require matter to transmit energy 24

25. Media and Wave Speed The more densely packed the matter, the more quickly the energy is transmitted Sound travels more quickly through solids than through liquids or gases 25

26. Media and Wave Speed When waves travel through gases, the temperature of he media affects the wave speed of sound waves. The higher the temperature of the gas, the faster the particles will move Light and other types of electromagnetic waves do not require matter to transmit energy 26

27. Media and Wave Speed In a vacuum all electromagnetic waves travel at the same speed, 300,000 kilometers per second When such waves encounter matter, their speed will change, depending upon how they interact with the matter 27