1. Electromagnetic Waves
AP Physics
Chapter 22

2. Vibration and Waves
22.1 Maxwell’s Equations

3. After the work of Oerseted, Ampere and Faraday
22.1 Maxwell’s Equations
After the work of Oerseted, Ampere and Faraday
James Clark Maxwell – all
electric and magnetic
phenomena can be
described by four equations
Fundamental – even taking into account relativity
Require Calculus
22.1

4. Gauss’s Law – relates electric field to electric charge
22.1 Maxwell’s Equations
Gauss’s Law – relates electric field to electric charge
Magnetic field Law –
Faraday’s Law – electric field is produced by magnetic field
Ampere’s Law – magnetic field produced by an electric current, or changing electric field
22.1

5. 22.2 Production of Electromagnetic Waves
Vibration and Waves
22.2 Production of Electromagnetic Waves

6. 22.2 Production of Electromagnetic Waves
How Electromagnetic Waves are Produced
The charged particle oscillate
As it travels one direction a current is produced
This generates a magnetic field
When the direction changes, so does the current and the magnetic field
EMR Production
22.2

7. 22.2 Production of Electromagnetic Waves
Electric and magnetic fields are perpendicular to each other
The fields alternate in
direction
These are
electromagnetic waves
Transverse
In general – accelerating electric charges give rise to electromagnetic waves
22.2

8. 22.3 Electromagnetic Spectrum
Vibration and Waves
22.3 Electromagnetic Spectrum

9. S-93
A hamster is out driving his fancy hamster wheel and yelling at a frequency of 1200 Hz. He approaches an observer at 65 m/s. If the observer runs away at 27 m/s, what is the apparent frequency that the observer hears? Assume that the air temperature is 27.5oC.

10. 22.3 Electromagnetic Spectrum

11. 22.3 Electromagnetic Spectrum
All EMR has a velocity of
in a Vacuum
Velocity decreases with increase in
optical density
The wave equation becomes
Unlike Sound – energy depends on frequency
22.3

12. What are the next two harmonics that the French horn would produce?
A mouse name Henry (French) plays a French Horn. If the air temperature is 22oC
How long would the horn have to be to play 512 Hz as its fundamental frequency. Assume that it acts like a closed tube.
What would be the velocity and wavelength of that frequency in the air?
What are the next two harmonics that the French horn would produce?

13. Next time you feel overweight, think of this cat. He has big bones.
Good Luck on Your Test