1. Chapter 3– Electromagnetic Waves
3.1 The Nature of Electromagnetic Waves

2. I. Essential Question:
What is an electromagnetic wave?

3. II. Key Vocabulary
Electromagnetic wave: a transverse wave that involves electric and magnetic energy.
Electromagnetic radiation: the energy from electromagnet waves through space.
Polarized light: light that passes through a filter.
Photoelectric effect: when light moves so much energy it causes an electron to leave a metal.
Photon: a packet of light energy

4. III. Key Concepts
An EM wave is made up of vibrating electric and magnetic fields that move through space/medium at the speed of light.
The movement of charged particles creates a vibrating electric field, which then produces a vibrating magnetic field.
EM waves do not need a medium, so they can travel in a vacuum or empty space.

5. III. Key Concepts The wave model:
Ordinary light has waves that vibrate in all directions.
A polarizing filter creates tiny slits that allows light to only travel in one direction, resulting in polarized light.

6. III. Key Concepts The particle model:
Sometimes light behaves like a stream of particles.
The stream of particles, or photons, can have enough energy to knock electrons away from metals.

7. Chapter 3 – Electromagnetic Waves
3.2 Waves of the electromagnetic spectrum

8. I. Essential Question: How do electromagnetic waves compare?
What makes up the electromagnetic spectrum?

9. II. Key Vocabulary
Electromagnetic spectrum: complete range of EM waves in order of increasing frequency.
Radio waves: EM waves with the longest wavelengths and lowest frequencies.
Microwaves: next on the EM spectrum after radio waves.
Radar: system that uses reflected microwaves to detect objects and measure distance/speed.
Radio detection and ranging
Infrared rays: next on the EM spectrum after microwaves.

10. II. Key Vocabulary
Thermogram: an image that shows regions of different temps in different colors.
Visible light: EM waves you can see.
Ultraviolet rays: next on the EM spectrum after visible light.
X-rays: next on the EM spectrum after UV rays.
Gamma rays: the EM waves with the shortest wave length and highest frequency.

11. III. Key Concepts
All EM waves travel at the same speed in a vacuum, but they have different wavelengths and frequencies.
As the wavelength decreases, frequency increases.
Waves with a higher frequency also carry a higher energy.

12. III. Key Concepts
Infrared rays are sometimes called heat rays because you can feel the heat from them.
Warmer objects give off more energy than cooler objects.
Visible light that appears white is a mixture of all of the colors.
The visible light goes ROYGBIV – red has the longest wave length (least energy) of the colors.

13. III. Key Concepts
UV rays can damage or kill living cells with too much exposure, but are useful in causing skin cells to produce Vitamin D.
Dense matter absorbs X-rays, which stops it from passing through. This is why it is used to detect broken bones.
Gamma rays can be used to study internal structures of the body; too much is harmful to the body.

14. Chapter 3 – Electromagnetic Waves
3.3 Wireless Communication

15. I. Essential Question:
How do electromagnetic waves work with technology?

16. II. Key Vocabulary
Amplitude modulation: method of broadcasting signals by changing the amplitude of a wave (AM)
Frequency modulation: method of broadcasting signals by changing the frequency of a wave (FM)

17. III. Key Concepts
Radio waves carry info from the antenna at a broadcasting station to the antenna on your radio.
AM waves have a constant, low frequency and energy and can be broadcasted over long distances.
FM waves have a constant amplitude, high frequencies, and cannot travel as far as AM waves.

18. III. Key Concepts
Cell phones work because areas are divided into small cells which have one or more towers to relay signals to a central hub.
Cell phones work by transmitting and receiving high frequency microwaves.
Your cell phone service depends on terrain (why?) and how close you are to a tower/hub.

19. III. Key Concepts
Communication satellites receive and send signals to radio, TV, and telephone systems.
GPS uses a network of 24 satellites that broadcast radio waves to Earth.
Signals from 4 out of 24 satellites are used to detect your location; 3 of them tell where you are and 1 tells how far above Earth’s surface you are.