EM waves and uses

• microwaves are used by satellites
• communication to and from satellites uses microwaves, best to use microwaves that pass easily through the earths water atmosphere
• for satellite TV, signal from a transmitter is transmitted into space
• when the transmitter is picked up by satellite receiver dish orbiting thousands of kilometres above the earth. the satellite transmits the signal back to earth in a different direction
• when it's received by a satellite dish on the ground. There is a slight time delay between the signal being sent and received because of the long distance the singal has to travel
• in microwave ovens, the microwaves are absorbed by water molecules in food, then transferred the energy they are carrying causing the water to heat up
• the water molecules then transfer this energy to the rest of the molecules in the food by heating - quickly cooks the food
• infrared radiation is given out by all hot object - the hotter the object, the more IR radiation given out
• infrared cameras can be used to detect infrared radiation and monitor temperature. the camera detects IR radiation and turns it into an electrical signal which is displayed on a screen. the hotter the object, the brighter it appears
• absorbing IR radiation causes objects to get hotter. Food can be cooked using IR radiation.
• electric heaters contain long piece of wire that heats up when a current flows through it. this wire emits lots of IR radiation, which is absorbed by objects and the air in the room. energy is transferred by the IR waves to the thermal energy stores of the objects, causing their temperature to increase