Download Chapter 12 - St. Ambrose School

Chapter 12 – Electromagnetic Waves (EM)
Overview: The Sun constantly emits energy as electromagnetic waves. However, the human eye cannot see some of
these waves.
Lesson 1
Electromagnetic Wave: a wave that can travel through empty space and through matter
Radiant Energy: energy carried by an electromagnetic wave

The Sun is not the only source of radiant energy.
Electromagnetic waves form when an electric charge accelerates by either speeding up, slowing down, or changing
direction.
Force Field: an electric field surrounds a charged particle
Connected Fields: Electric fields and magnetic fields are related:
A changing electric field produces a magnetic field.
A changing magnetic field produces a changing electric field.
Properties of Electromagnetic Waves
Wavelength: The distance between one point on a wave to the nearest point just like it.
Frequency: the number of wavelengths that pass by a point in a certain period of time.
*electromagnetic waves are grouped according to wavelength and frequency.
Wave Speed: Electromagnetic waves travel through space at 300,000 km/s or the speed of light.
Calculate a wave’s speed: frequency multiplied by its wavelength.
Calculate a wave’s wavelength moving through space: divide the speed of light by the frequency of the wave.
Sources of EM:
The Sun is the Earth’s most important energy source.
Moon
Stars
Planets
Sources of EM on Earth:
Campfire
a lightbulb
burner on an electric stove
Lesson 2
Electromagnetic spectrum: the entire range of electromagnetic waves with different frequencies and wavelengths
Classifications of EM Waves:
Radio – low frequency, low energy
Microwave - low frequency, low energy
Infrared – wavelength is short than microwave but longer than light
Light – EM waves that your eyes can see: ROGBIV
Ultraviolet – slightly shorter wavelength and higher frequency than light; carries enough energy to cause
chemical reactions
X-Rays – high energy EM that has a slightly shorter wavelength and higher frequency than an ultraviolet wave
Gamma Rays – high energy EM with a shorter wavelength and higher frequency than all other types of EM
Lesson 3
Using Electromagnetic Waves
Radio:
Broadcasting: the use of electromagnetic waves to send information in all directions
Radio and Television:
Carrier Wave: an electromagnetic wave that a radio or television station uses to carry its sound or image signals.
Signals are modulated
Amplitude Modulations (AM): A change in the amplitude of a carrier wave
Frequency Modulations (FM): A change in the frequency of a carrier wave
Microwaves:
Communications Satellites:
Global Positioning System (GPS) – a worldwide navigation system that uses satellite signals to determine a
receiver’s location
Infrared Waves:
Infrared Imaging – thermal cameras that detect infrared waves rather than light waves
Imaging Earth – using infrared to display variations in vegetation, snowfall, weather, volcanic activity, etc
Light:
Sun provides most of Earth’s light, but light emitted on Earth also ahs uses.
Ultraviolet Waves (UV):
Can cause skin damage, cause certain materials to glow when exposed to UV, UV can be used to sterilize or kill
germs, has medical uses too
X-Rays:
Can pass through matter; used for security and medical imaging
Gamma Rays: High energy can be used to destroy diseased tissue in a patient.