EM waves and their uses Flashcards
What uses microwaves and why ?
communication to and from satellites use microwaves
- pass easily through earth watery atmosphere
How does a satellite tv work ?
signal from transmitter is transmitted into space where its picked up by satellite receiver dish orbiting thousands of km above the earth.
Satellite dish transmits the signals back to earth is different direction.
where its received by satellite dish on ground.
There is a slight time delay between signals being sent and received because of the long distance needed to travel.
How do microwave ovens use microwaves ?
microwaves absorbed by water molecules in food.
The microwaves are penetrated up to a few cm into the food before being absorbed and transferring energy they’re carrying to water molecules in food = causing water to heat up.
Water molecules transfer energy to rest of food by heating - which quickly cooks the food
What objects give out infrared radiation ?
all objects
Hotter object = more IR radiation they give out
Role of infrared cameras
Detect IR and monitor temperature . Camera detects IR and turns it into electrical signals displayed on screen as picture. Hotter object, brighter it appears
What occurs to an object as it absorbs IR ?
get hotter = Food can get cooked with IR radiation = temp of food rises as IR is absorbed
How do electrical heaters heat rooms ?
they contain long piece of wire which heats up when current passes through it. Wire emits lots of IR which is absorbed by object and air in room
Energy is transferred by IR waves to thermal energy store of objects = temp increase
