# Mobile phones

Discussion in 'Science' started by pink_reindeer, Mar 4, 2012.

1. ### pink_reindeerOccasional commenter

How do they work? How can pupils explain energy loss (e.g. masts/satellites/wires)? How can they compare to another familiar example (e.g. Sky tv)? How can they describe energy transfers happening in another machine, e.g. fibre optic cables?

This is an assessed task, and I have just copied (and translated) some of the key points. I was hoping you could help me. I have some ideas, but as a non physicist I want to make sure I'm on the right track. Thanks.

2. ### blazerStar commenter

Don't phones use a shorter wavelengthof mocrowaves than the ovens? The holes in the mesh inside the door have a diameter less than half the wavelegth of the waves used in the oven thus preventing them getting out. Shorter wavelengths may be able to pass through.

3. ### aldebaran

shorter wavelength = higher frequency = more energy

even more reason not to hold them to your ear?

4. ### decibelFarad

How do they work?

UHF Radio waves, much the same as an FM radio (voice) or wifi router (data). These are modulated to a digital form and, iirc switched from frequency to frequency depending on the cell tower.

How can pupils explain energy loss (e.g. masts/satellites/wires)?

Inverse square law? Slightly more complex than this as the transmitting energy depends on proximity to tower
.
How can they compare to another familiar example (e.g. Sky tv)?

The frequency, hence bandwidth is less, For Video you require higher rates of data transmission than voice/ text.

How can they describe energy transfers happening in another machine, e.g. fibre optic cables?

Electrical energy to light (IR) and heat, light back to electrical energy. Demo showing an IR remote using a camera phone and the flashing nature of the pulses.

5. ### blazerStar commenter

Blimey, KS2 gets harder every year!