1. Wave Behavior

2. PERFORMANCE INDICATOR
8.P.3A.3
Analyze and interpret data to describe the behavior of waves (including refraction, reflection, transmission, and absorption) as they interact with various materials.

3. 1. Reflection
Reflection- When a wave strikes an object or surface and bounces off.
Ex: Echo is reflected sound waves
Ex: Mirror reflects light waves
If smooth surface the reflected image is clear and sharp
If rough or uneven the reflected image is distorted because reflected light scatters

4. Reflection Reflect means bounces off of
Regular reflection – rays of light hit a smooth surface and the rays are reflected back at the same angle.
Diffuse reflection – rays of light hit a bumpy or uneven surface which causes the rays to bounce back at different angles

5. CHECK POINT WHAT IS REFLECTION? WHAT ARE THE TWO TYPES OF REFLECTION?
WHEN rays of light hit a smooth surface and the rays are reflected back at the same angle WHAT IS THIS CALLED?

6. Reflection and Types of Mirrors
Plane mirrors are a flat sheet of glass, that has a silver-colored coating on one side
the coating reflects the light
The coating is smooth = regular reflection occurs and a clear image forms
Image is a copy of an object formed by reflected or refracted rays of light

7. What kind of image forms:
Virtual images are upright images that forms where light seems to come from
Virtual = something that does not really exist
Plane mirrors produce virtual images that are upright and the same size as the object
Image not exactly same as object
The left and right of the image are reversed

8. Concave Mirrors Concave mirrors can form virtual or real images
A mirror with a surface that curves inward like the inside of a bowl is a concave mirror
Reflects parallel rays of light so that they meet at a point
Concave mirrors can form virtual or real images

10. Real Vs. Virtual Images Real images form when rays actually meet
Occur if the object is farther away from the mirror than the focal point
May by larger or small than the object
Virtual images form when the object is between the mirror and focal point
are always larger than the object for concave mirrors

11. Convex Mirrors
Convex Mirrors are mirrors with surfaces that curve outwards
rays spread out but appear to come to from a focal point behind the mirror
Because rays never meet, images formed by convex mirrors are always virtual and smaller than the object
Used in car mirrors
Advantage: allows you to see a larger area than you can with a plane mirror
Disadvantage: images appears further away than it really is

12. CHECK POINT THE MIRROR IN YOUR BATHROOM IS WHAT KIND?
WHAT KIND OF MIRRORS ARE ALWAYS VIRTUAL?
WHAT KIND OF MIRRORS CAN PRODUCE REAL AND VIRTUAL IMAGES?

13. PERFORMANCE INDICATOR
8.P.3A.3
Analyze and interpret data to describe the behavior of waves (including refraction, reflection, transmission, and absorption) as they interact with various materials.

14. 2. Refraction of Light
Refraction is the bending of a wave as it passes from one medium to another.

15. What causes the light to bend?
What’s different about air and water?
DENSITY – the amount of mass in a certain volume of a substance (mass/volume)
WATER
AIR
gas
liquid

16. Example of Refraction
When a straw is placed in water it looks like this:
In this case the light rays are slowed down by the water and are bent, causing the straw to look broken. The two mediums in this example are air and water.

17. Another Example:
When you use a magnifying glass, the object appears larger because of refraction.
The light waves traveling in the air change direction when they enter the glass of the lens, and then again when they move from the glass back into the air again.
Lens

18. CONVEX LENS – CONVERGING LENS

19. Convex Lens A convex lens is shaped like two half circles, thin at the edge and thick at the middle. A convex lens is converging and can produce virtual and real images.

20. CONCAVE LENS - DIVERGING LENS

21. Concave Lens A concave lens is thin at the center and thick at the edges. Concave lenses only produce virtual images They are diverging lenses.

22. CHECK POINT HOW IS REFRACTION DIFFERENT FROM REFLECTION?
WHAT IS A MEDIUM? GIVE 3 EXAMPLES
WHAT IS MORE DENSE: AIR OR WATER? WHY?

23. PERFORMANCE INDICATOR
8.P.3A.3
Analyze and interpret data to describe the behavior of waves (including refraction, reflection, transmission, and absorption) as they interact with various materials.

24. 3. Diffraction of Light
Diffraction is the bending, spreading, and interference of waves when they go through a narrow opening.

25. Diffraction Patterns
Radio waves can diffract around hills, mountains or even the whole planet.
Light waves can diffract through tiny slits.
X-rays can diffract around atoms.

26. Electromagnetic waves have a huge range of wavelengths.
If the wavelength is of a similar size to a gap in a harbor wall, then the wave will diffract as shown below.

27. If the wavelength does not match the size of the gap, then only a little diffraction will occur at the edge of the wave.

28. DIFFRACTION VS REFRACTION
Diffraction and refraction both cause waves to bend. The difference is that refraction occurs when waves pass through an object, while diffraction occurs when waves pass around an object.

29. PERFORMANCE INDICATOR
8.P.3A.3
Analyze and interpret data to describe the behavior of waves (including refraction, reflection, transmission, and absorption) as they interact with various materials.

30. 4. Transmission of Light
Transmission is the passing of waves through a medium.

31. Think about a radio station…
An electromagnetic wave is produced.
The wave travels from the stations transmitter out in all directions at the speed of light.
Even though you cannot hear radio waves when your radio’s turned off, the waves are still being transmitted in the room.

32. Many materials are classified by how well they transmit light.
Three Types of Materials:
Transparent
Translucent
Opaque

33. Transparent Materials
When light passes straight through a material, that material is transparent.
Transparent materials you can see completely through.

34. Translucent
Materials that are translucent and allow some light to pass but the light cannot be clearly seen through

35. Opaque
A material that allows no light to pass through

36. Opaque objects:
Heavy weight paper,
Cardboard
Aluminum foil,
bricks, buildings,
Your eyelids and hands,
Solid wood door,
All of these objects are opaque because light cannot pass through them at all.
They cast a dark shadow.

37. CHECK POINT ALL OF THE FOLLOWING ARE OPAQUE MATERIALS EXCEPT:
aluminum foil; brick; bulb; wood
A MATERIAL THROUGH WHICH LIGHT CANNOT PASS IS CALLED:
NAME THE THREE MATERIALS ARE CLASSIFIED BY HOW THEY TRANSMIT LIGHT

38. PERFORMANCE INDICATOR
8.P.3A.3
Analyze and interpret data to describe the behavior of waves (including refraction, reflection, transmission, and absorption) as they interact with various materials.

39. POLARIZATION
when the displacement of a transverse wave is in a specific orientation or direction
 familiar example: polarized sunglasses
polarized materials only allow waves that correspond to a special direction to pass through

40. Interference Waves interfere with each other.
Interference- When two waves combine and form a new wave when they overlap
Interference may be constructive. In transverse waves, a crest will interfere with another crest constructively to produce a larger crest and a trough will interfere with another trough to produce a larger trough.
Constructive interference makes sound louder.
Waves with larger amplitudes carry more energy. Ex: Ocean Waves

42. Interference (Continued)
Interference may be destructive.
A crest will interfere with a trough to lessen or cancel the displacement of each.
Compressions interfere with rarefactions to lessen or cancel the displacement of each.
Destructive interference creates smaller waves and makes sounds quieter. Ex. Noise-cancelling headphones

44. BEATS: INTERFERENCE Overlapping waves of different f (frequencies)
In music interference creates “beats” (changes in loudness & softness)
Wave 1 (red) and Wave 2 (blue) combine to form beat pattern (in green) High amplitude = LOUD Low amplitude = soft

45. STANDING WAVES
A standing wave is a wave that appears to stand in one place, even though it is two waves interfering as they pass through each other.

46. Nodes and Antinodes
In a standing wave, destructive interference produces points with zero amplitude, called nodes.
The nodes are always evenly spaced along the wave.
At the points in the standing wave where constructive interference occurs, the amplitude is greater than zero.
Points of maximum amplitude on a standing wave are called antinodes.

48. DOPPLER EFFECT
the shift in frequency of wave when a wave source and an observer are moving relative to each other
A stationary bug producing disturbances in water
A• • B
A bug moving to the right and producing disturbances
A• •B
Notice how waves near B are “compressed” → ƒ higher
Waves “leaving” A are “expanded” → ƒ lower
apparent increase in ƒ for observers as the source approaches/ moves closer to observer
apparent decrease in ƒ for observers as the source recedes / moves away from observer

49. DOPPLER EFFECT: SOUND Longer λ for observers as train leaves
Shorter λ for observers as train approaches

50. DOPPLER EFFECT: LIGHT
Longer λ for observers as train leaves = light shifts RED
Shorter λ for observers as train gets closer = Light shifts BLUE

51. CHECK POINT
WHAT KIND OF INTERFERENCE IS A BELOW?
A B

52. Absorption
Absorption of light happens when atoms in an object absorb (take in and hold) the light waves.
For example: You are able to see a red apple because all of the other light waves are absorbed but red is reflected to your eyes.