# Homework Help: Electromagnetic waves practical applications and properties

1. Feb 8, 2013

### kiwi101

Applications:
garage door openers: 40.0 ,
standard cordless phones: 40.0 to 50.0 ,
baby monitors: 49.0 ,
FM radio stations: 88.0 to 108 ,
cell phones: 800 to 900 ,
Global Positioning System: 1227 to 1575 ,
microwave ovens: 2450 ,
wireless Internet technology: 2.4 to 2.6 .

Which of the following statements correctly describe the various applications listed above?
Check all that apply.

1.All these technologies use radio waves, including low-frequency microwaves.
2.All these technologies use radio waves, including high-frequency microwaves.
3.All these technologies use a combination of infrared waves and high-frequency microwaves.
4.Microwave ovens emit in the same frequency band as some wireless Internet devices.
5.The radiation emitted by wireless Internet devices has the shortest wavelength of all the technologies listed above.
6.All these technologies emit waves with a wavelength in the range 0.10 to 10.0m .
7.All the technologies emit waves with a wavelength in the range 0.01 to 10.0km .

My attempt at a solution was choosing 1,4,5 and 7.
This combination is wrong.
I am very sure about one because we do use short frequency microwaves and I am also sure about 7. The rest I found sources online confirming what I believe.

Help would be appreciaited.

2. Feb 9, 2013

### Simon Bridge

Go through each of them one at a time and see if there are any exceptions.
Compare with your notes for the electromagnetic spectrum - eg. write down the frequency ranges where they are named.

What are the units for each of the numbers in the list?
The units are important - look at #7 ... as you wrote it, it says 0.01-10.0km which implies 0.01km - 10.0km.