1. Light and the Electromagnetic Spectrum

2. Electromagnetic Waves
All electromagnetic waves travel at the same speed through space (the speed of light)
Gamma rays, X-rays, Ultra-violet waves, Light, Infra-red rays, Microwaves, and Radio waves are all electromagnetic waves with different wavelengths
Some substances absorb EM waves, some reflect them and others transmit them
KEY POINTS

3. What is Light & EM Waves

4. Electromagnetic Energy/Waves
The sun is the source of light on planet Earth
It produces electromagnetic (EM) energy that travel at light speed – 186,000 miles per second or 300,000 Km/s
It produces light & heat!

5. Electromagnetic Energy from the Sun is produced by Nuclear Reactions within the Sun
Two hydrogen (H) atoms fuses into Helium (HE) and energy is released!

6. Why does only a tiny fraction of the sun’s energy provide heat for the Earth??
Most of the energy we get, comes as light from the Sun as Visible light (the stuff we can see).
Some is higher energy (i.e., more energy per photon) ultraviolet light and some of it is lower energy infrared radiation.
But, most is middle-of-the-road visible light. What happens to this light? Most of it bounces off us right back out into the blackness of space. But, some of it gets absorbed.

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

8. Electromagnetic waves travel VERY FAST – a round 300,000 kilometres per sec second (the speed of light).
At this speed they can go around the world 8 times in one second.

9. What is the speed of EM waves?
All EM waves travel 300,000 km/sec in space. (speed of light-nature’s limit!)
EM waves usually travel slowest in solids and fastest in gases.
Material
Speed (km/s)
Vacuum
300,000
Air
<300,000
Water
226,000
Glass
200,000
Diamond
124,000

10. The Electromagnetic Spectrum
The electromagnetic spectrum represents the range of energy from low energy, low frequency radio waves with long wavelengths up to high energy, high frequency gamma waves with small wavelengths.

11. Frequency Ranges Wavelengths Frequencies (cycles per sec)
Frequencies (cycles per sec)
3 x x x x x x10 22

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

13. Radio Waves

14. 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.

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

16. Microwaves

17. Have shorter wavelengths and higher frequency than radio waves.
MICROWAVES
Have shorter wavelengths and higher frequency than radio waves.

18. 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.

19. 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.

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

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

22. 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.

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

24. The colors we see in objects are the colors that are reflected, all other colors are absorbed. A red t-shirt appears red because red is reflected to our eyes and the other colors are absorbed.
When all colors are being reflected we see white light (white isn’t really a color)

25. When all wavelengths of light are being absorbed we see black (black also, isn’t really a color)
A false-color image is made when the satellite records data about brightness of the light waves reflecting off the Earth's surface.

26. 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.

27. At station 7, what color warmed up more or at a faster rate?

28. Radiometer The bulb in which the blades spin is a partial vacuum.
So, air has something to do with it. Basically, the principal is the air that hangs out by the cool side of the blade flows slowly to the warm side of the blade. That process is called thermal transpiration. Science is cool.

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

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

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

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

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

34. 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)

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

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

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

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

39. Exploding nuclear weapons emit gamma rays.

40. 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.