Explain how EM waves differ from mechanical waves.

·  EM waves: disturbance in a field, can travel through a vacuum, travel at the speed of light

·  Mechanical waves: disturbance in a medium, cannot travel through a vacuum (only matter), must give up energy as it moves

Identify the sources of EM waves.

·  2 sources of EM waves on Earth: the Sun and human technology

Recognize how EM waves transfer energy.

·  In a vacuum, EM waves move potential energy from one place to another

·  In a material medium, they can both move potential energy and convert energy into other forms.

Distinguish how EM waves differ from one another.

·  The various types of EM waves differ from each other in their wavelengths and frequencies.

·  Long wavelengths and low frequencies

o  Radio waves: longest wavelengths, lowest frequencies, and the lowest energies

o  Microwaves: shorter wavelengths, higher frequencies, and higher energy than radio waves

·  Mid-range wavelengths and frequencies

o  Visible light: part of the EM spectrum that human eyes can see; it lies between 1014 Hz and 1015 Hz

o  Infrared light: EM frequencies between microwaves and visible light

o  Ultraviolet light: frequencies above those of visible light and partially below those of x-rays; because UV light has higher frequencies than visible light, it also carries more energy

·  Short wavelengths and high frequencies

o  X-rays: frequencies from about 1016 Hz to 1021 Hz

o  Gamma rays: frequencies from about 1019 Hz to more than 1024 Hz

Describe how different types of EM waves are used.

·  Radio waves: telecommunication (communication over long distances) with radio transmitter, radio stations, broadcast television

·  Microwaves: radar and cell phones

·  Infrared light: infrared lamps, infrared rays from a toaster, infrared scopes and cameras

·  Ultraviolet light: sterilize medical instruments and food; causes skin cells to produce vitamin D; used to treat skin problems

·  X-rays: x-ray images for diagnosing bone fractures and finding dense tumors

·  Gamma rays: doctors use to kill cancer cells and fight tumors