Transferring Energy

Microwaves: 

• Absorbed by water and fat molecules on the outside of the food, it increases kinetic energy of particles. 
• The energy is transferred to the rest by conduction and convection.
• Used to transmit information over large differences in line of sight.
• Poor signals happen when areas are out of sight.
• Mobile phones and mirowave oven don't use the same wavelengths, there are concerns that mobile phones can cause harm. There are also public concerns about transmission masts.
• Microwaves signals can be lost and affected by: Large objects, (microwaves don't diffract), poor weather conditions, large areas of water, the curvature of the Earth and interferance of signals.
• You can reduced problems by: Limiting transmitter distances, and building masts higher up on high buildings and things.

Infrared:

• Absorbed by all of the particles on the surface of the food, increasing the kinetic energy of particles.
• Energy transferred by conduction and convection to the rest of the food.
• Examples of usage: Remote controls, sensors, short-distance wireless data links, burglar alarms and security lights.
• TV's use digital codes. The amount of energy in the wave depends on frequency and the dangers.

Analouge signals:

• Used to transmit data, they vary in amplitude.
• Can have any value within a fixed range.
• Poor signal quality due to interference.

Digital signals:

• Can be used to transmit data as a series of pulses.
• The value do not vary. Only 2 states, on (1) and of (0). 
• They suffer from interference but it doesn't affect the signal.
• High signal quality because interference is removed.

Wireless communication:                                                                                                      Advantages:

• No connection to a phone land-line needed.
• Portable, can be used anywhere.

Disadvantages:

• Aerials are needed to pick signals up.