1. Light and Electromagnetic Waves & the Electromagnetic Spectrum

2. Light and the Eye

3. NATURE OF WAVES
© 2000 Microsoft Clip Gallery
Waves (Def.) – A wave is a disturbance that transfers energy through vibrations.
Medium/Matter – Substance or region through which a wave is transmitted.
Speed of Waves – Depends on the properties of the medium.

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

5. Light travels VERY FAST – around 300,000 kilometres per second.
At this speed it can go around the world 8 times in one second.

6. Light travels much faster than sound. For example:
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.

7. http://studyjams. scholastic

8. Properties of Light When light strikes an object it is: Reflected
Transmitted
Absorbed

9. Properties of Light Color of objects is the color it reflects
Ex- an orange is orange because it absorbs every color BUT orange, instead it reflects orange
If you do not shine orange light on it, it will appear black
Black is the absence of color, white is the blending of all colors

10. Properties of Light
Reflection- when an object or wave bounces back off a surface

11. Properties of Light
Reflection- when an object or wave bounces back off a surface Law of reflection- angle made from incoming wave = the angle made from reflected wave

12. Properties of Light
Refraction- bending of light waves due to a change in speed

13. LIGHT: Refraction of Light
Refraction – Bending of light due to a change in speed.
Index of Refraction – Amount by which a material refracts light.
Prisms – Glass that bends light. Different frequencies are bent different amounts & light is broken out into different colors.

14. Properties of Light
Refraction- bending of light waves due to a change in speed Lens- curved glass or transparent material that refracts light Convex lens- thicker in the center than the edges (bends light in)

16. http://studyjams. scholastic

17. PowerPoint created by Mrs. B-D 2007
Light, Lens, Action!
From the moment you wake up in the morning to the time you go to sleep at night, your eyes are acting like a video camera. Everything you look at is then sent to your brain for processing and storage much like a video. This is a very simplified explanation, but as you read on, you will discover why the sense of sight is actually considered the most complex of the five senses.
PowerPoint created by Mrs. B-D 2007

18. PowerPoint created by Mrs. B-D 2007
How the Eye Works
Take a moment to locate an object around you. Do you know how you are able to see it? Would you believe that what you are actually seeing are beams of light bouncing off of the object and into your eyes? It is hard to believe, but it is true.
The light rays enter the eye through the cornea, which is a thick, transparent protective layer on the surface of your eye. Then the light rays pass through the pupil (the dark circle in the center of your eye) and into the lens.
PowerPoint created by Mrs. B-D 2007

19. How the Eye Works continued
Your lens in your eyes change size all the time. When you look at objects real close up, the lens gets thicker. If you look at objects far away, it gets thinner. It does this to help you focus the correct image on the retina.
After light passes through the lens it shines through the back of the eye where it hits the retina. The retina takes the light and changes it into nerve impulse so the brain can understand what the eye sees. It sends the message to the brain by way of the optic nerve.
PowerPoint created by Mrs. B-D 2007

20. PowerPoint created by Mrs. B-D 2007
Parts of the Eye
PowerPoint created by Mrs. B-D 2007

21. PowerPoint created by Mrs. B-D 2007
Cornea: The cornea is a clear white covering over the outside of the eye. It helps the eye focus like a lens on a camera.
Iris: The iris is the part of your eye that has color. It gets bigger and smaller to let in different amounts of light.
Pupil: Black opening in the middle of the eye. Light comes through this opening.
PowerPoint created by Mrs. B-D 2007

22. PowerPoint created by Mrs. B-D 2007
Lens: The lens bends light. This helps the eye see close up and far away things.
Retina: The retina has nerve cells called rods and cones that detect light. It is in the back of your eye.
Optic Nerve: The optic nerve carries electrical signals from your retina to your brain so you can see.
PowerPoint created by Mrs. B-D 2007

23. PowerPoint created by Mrs. B-D 2007
Rods and Cones
Rods and cones are special cells that process light.
Rods and cones are extremely small. In fact, there are about 120 million rods and 7 million cones in each eye!
Rods help us see black and white and shades of grey.
Cones help us see color. You have three kinds of cones are - red, green, and blue. These cones work together to help us see millions of colors.
PowerPoint created by Mrs. B-D 2007

24. PowerPoint created by Mrs. B-D 2007
Flipped Image
When you see images, they turn upside down when they hit the retina. So your brain sees everything in the world upside down. Your brain basically flips everything around so it is right side up again.
PowerPoint created by Mrs. B-D 2007

26. Electromagnetic
Spectrum

27. Electromagnetic Waves
Transverse waves without a medium!
(They can travel through empty space)

28. They travel as vibrations in electrical and magnetic fields.
Have some magnetic and some electrical properties to them.

29. When an electric field changes, so does the magnetic field
When an electric field changes, so does the magnetic field. The changing magnetic field causes the electric field to change. When one field vibrates—so does the other.
RESULT-An electromagnetic wave.

30. Waves or Particles?
Electromagnetic radiation has properties of waves but also can be thought of as a stream of particles.
Example: Light
Light as a wave: Light behaves as a transverse wave which we can filter using polarized lenses.
Light as particles (photons): When directed at a substance light can knock electrons off of a substance (Photoelectric effect)

31. Electromagnetic Spectrum—name for the range of electromagnetic waves when placed in order of increasing frequency
GAMMA RAYS
ULTRAVIOLET RAYS
RADIO WAVES
INFRARED RAYS
X-RAYS
MICROWAVES
VISIBLE LIGHT

32. Notice the wavelength is
long (Radio waves) and gets shorter (Gamma Rays)

34. RADIO WAVES
Have the longest wavelengths and lowest frequencies of all the electromagnetic waves.

35. Global Positioning Systems (GPS) measure the time it takes a radio wave to travel from several satellites to the receiver, determining the distance to each satellite.

36. A radio picks up radio waves through an antenna and converts it to sound waves.
Each radio station in an area broadcasts at a different frequency.
# on radio dial tells frequency.

37. (MAGNETIC RESONACE IMAGING)
MRI
(MAGNETIC RESONACE IMAGING)
Uses Short wave radio waves with a magnet to create an image.

38. MICROWAVES
Have the shortest wavelengths and the highest frequency of the radio waves.

39. Used in microwave ovens.
Waves transfer energy to the water in the food causing them to vibrate which in turn transfers energy in the form of heat to the food.

40. RADAR (Radio Detection and Ranging)
Used to find the speed of an object by sending out radio waves and measuring the time it takes them to return.

41. Shorter wavelength and higher frequency than microwaves.
INFRARED RAYS
Infrared= below red
Shorter wavelength and higher frequency than microwaves.

42. You can feel the longest ones as warmth on your skin Warm objects give off more heat energy than cool objects.

43. Heat lamps give off infrared waves.
Thermogram—a picture that shows regions of different temperatures in the body. Temperatures are calculated by the amount of infrared radiation given off.
Heat lamps give off infrared waves.
Therefore people give off infrared rays.

44. VISIBLE LIGHT
Shorter wavelength and higher frequency than infrared rays.
Electromagnetic waves we can see.
Longest wavelength= red light
Shortest wavelength= violet (purple) light

45. When light enters a new medium it bends (refracts)
When light enters a new medium it bends (refracts). Each wavelength bends a different amount allowing white light to separate into it’s various colors ROYGBIV.

46. ULTRAVIOLET RAYS
Shorter wavelength and higher frequency than visible light
Carry more energy than visible light

47. Used to kill bacteria. (Sterilization of equipment)

48. Too much can cause skin cancer.
Use sun block to protect against (UV rays)

49. Causes your skin to produce vitamin D (good for teeth and bones)

50. X- RAYS Shorter wavelength and higher frequency than UV-rays
Carry a great amount of energy
Can penetrate most matter.

51. Bones and teeth absorb x-rays
Bones and teeth absorb x-rays. (The light part of an x-ray image indicates a place where the x-ray was absorbed)

52. Too much exposure can cause cancer
(lead vest at dentist protects organs from unnecessary exposure)

53. Used by engineers to check for tiny cracks in structures.
The rays pass through the cracks and the cracks appear dark on film.

54. GAMMA RAYS Shorter wavelength and higher frequency than X-rays
Carry the greatest amount of energy and penetrate the most.

55. Used in radiation treatment to kill cancer cells.
Can be very harmful if not used correctly.

56. The Incredible Hulk was the victim of gamma radiation.

57. Exploding nuclear weapons emit gamma rays.

58. Brief SUMMARY
A. All electromagnetic waves travel at the same speed. (300,000,000 meters/second) in a vacuum.
B. They all have different wavelengths and different frequencies.
Long wavelength-lowest frequency
Short wavelength highest frequency
The higher the frequency the higher the energy.