1. Electromagnetic Waves
Chapter 21A
Electromagnetic Waves

2. A changing electric field will produce a magnetic field
A changing electric field will produce a magnetic field. (Electromagnetic).
The speed of light (c ) is 3x108 m/s.
Visible light and all other electromagnetic waves consist of fluctuating electric and magnetic fields travelling at the speed of light (c ).

3. Electromagnetic (EM) Waves are Transverse Waves
The and fields are perpendicular to each other.
Both fields are perpendicular to the direction of motion
Therefore, em waves are transverse waves

4. The Spectrum of EM Waves
Different Forms of EM waves exist and are distinguished by their frequencies and wavelengths.
c = ƒλ
Wavelengths for visible light range from 400 nm to 700 nm (ROYGBIV in order from 700nm - 400nm)
Red, orange,yellow,green,blue,indigo,violet)

5. The EM Spectrum Visible light is a small portion of the spectrum
Types of EM waves are distinguished by frequency or wavelength.

6. Common EM Waves: Radio Waves Microwaves Infrared waves Visible light
The only part of the EM spectrum detected by the human eye.
Most sensitive at about 560 nm (yellow-green)

7. Ultraviolet light X-rays Gamma rays
Sun is an important source of uv light
Most uv light from the sun is absorbed in the stratosphere by ozone
X-rays
Gamma rays

8. Doppler Effect and EM Waves
A Doppler Effect occurs for em waves, but differs from that of sound waves
For light waves, the medium plays no role since the light waves do not require a medium for propagation.
The speed of em waves is the same in all systems.
Astronomers refer to a red shift when objects are moving away from the earth since the wavelengths are shifted toward the red end of the spectrum.