1. Properties of Light and the Electromagnetic Spectrum
Dan Flavin
Untitled (Marfa Project)

2. The speed of light
The speed at which light travels through air is approximately 300 million meters per second.
Light travels almost a million times faster than sound.
All electromagnetic waves travel at the speed of light. Visible light is just one type of electromagnetic wave.

3. Dual Nature of Light

4. Light is a Particle (Photon)
travels in straight lines at great speeds
is reflected from mirrors in a predictable way
Has energy in discrete packets, momentum
Photoelectric effect
Newton observed that the reflection of light from a mirror resembles the rebound of a steel ball from a steel plate

5. Photoelectric Effect

6. Light is a Wave Thomas Young showed that light is a wave, because it
undergoes diffraction and interference (Young’s double-slit experiment)
Wavelength l
Amplitude A
Frequency f

7. Light is a Wave
Click here for video
Click here for video

9. Polarization

10. Polarization

11. Polarization Polarization is another wave property of light.
The fact that light shows polarization tells us that light is a transverse wave.
Most of the light that you see is unpolarized.
That does not mean the light has no polarization.
Unpolarized light is actually an equal mixture of all polarizations.
We call ordinary light unpolarized because no single polarization dominates the mixture.

12. The Electromagnetic Spectrum
The energy field created by electricity and magnetism can oscillate and it supports waves that move.
These waves are called electromagnetic waves.

13. The Electromagnetic Spectrum
Electromagnetic waves have both an electric part and a magnetic part and the two parts exchange energy back and forth.
A 3-D view of an electromagnetic wave shows the electric and magnetic portions.

15. Visible Light as Part of the EM Spectrum
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16. RADIO WAVES
A. Have the longest wavelengths and lowest frequencies of all the electromagnetic waves.
B. A radio picks up radio waves through an antenna and converts it to sound waves.
C. Each radio station in an area broadcasts at a different frequency. # on radio dial tells frequency.
D. MRI (MAGNETIC RESONACE IMAGING)
Uses Short wave radio waves with a magnet to create an image

17. MRI of the Brain

18. AM=Amplitude modulation—waves bounce off ionosphere can pick up stations from different cities.
(535kHz-1605kHz= vibrate at 535 to 1605 thousand times/second) +

19. FM=Frequency modulation—waves travel in a straight line & through the ionosphere--lose reception when you travel out of range.
(88MHz-108MHz = vibrate at 88million to 108million times/second) +

20. MICROWAVES
Microwaves—have the shortest wavelengths and the highest frequency of the radio waves.
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.
Used by cell phones and pagers.
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.

21. INFRARED RAYS Infrared= below red
Shorter wavelength and higher frequency than microwaves.
You can feel the longest ones as warmth on your skin
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. 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
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.

24. The Electromagnetic Spectrum
The higher the frequency of the light, the higher the energy of the wave.
Since color is related to energy, there is also a direct relation between color, frequency, and wavelength.

26. ULTRAVIOLET RAYS
Shorter wavelength and higher frequency than visible light
Carry more energy than visible light
Used to kill bacteria. (Sterilization of equipment)
Causes your skin to produce vitamin D (good for teeth and bones)
Used to treat jaundice ( in some new born babies.
Too much can cause skin cancer.
Use sun block to protect against (UV rays)

27. X- RAYS Shorter wavelength and higher frequency than UV-rays
Carry a great amount of energy
Can penetrate most matter.
Bones and teeth absorb x-rays. (The light part of an x-ray image indicates a place where the x-ray was absorbed)
Too much exposure can cause cancer
(lead vest at dentist protects organs from unnecessary exposure)

29. GAMMA RAYS Shorter wavelength and higher frequency than X-rays
Carry the greatest amount of energy and penetrate the most.
Used in radiation treatment to kill cancer cells.
Can be very harmful if not used correctly.

30. Using the EM waves to view the Sun
Animation—View a Galaxy at different wavelengths

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