Topic 6 Em Waves And Rheur Uses Flashcards
What are microwaves used by
Satellite
What does communication to and from satellites use
Microwave which can easily pass through the earths watery atmosphere
For satellite TV where is the signal from the transmitter transmitted through
Through space
What picks up the signals
Satellite receiver dish opting thousands of kilometres above earth satellite transmits a signal back to earth in a different direction
Where is the signal from the satellite dish in space received
By satellite dish on the ground there is a slight time delay between single being sent and received because of the long distance the signal has a to travel
What are the microwave is absorbed by in microwave ovens
Water molecules in the food
The microwave penetrate up to a few centimetres into the food before doing what
Being absorbed and transferring energy that they’re carrying to the water molecules in the food cause in the water to heat up
What are the water molecules do with the energy
Transfer this energy to the rest of the molecules in the food by heating
What can infrared radiation be used for
To detect infrared or monitor temperature on infrared cameras
What is infrared radiation given off by
Hot objects
The hotter the object the
The more infrared radiation is given out
What can infrared cameras be used for
Detect the IR radiation and turns it into an electrical signal which is displayed on the screen as a picture
The hotter of the object is
The brighter it appears on the camera
What does absorbing infrared radiation cause
Objects to get hotter
What happens to the temperature of food as it absorbs infrared radiation
It increases
What do electric heaters contain
How long piece of wire that heats up when I current flows through it
What does the wires in electric heaters omit
Lots of infrared radiation
And a little visible light (the wire glows)
What is the emitted radiation absorbed by
The objects on the air in the room
What is energy transferred from the Ir waves to
The thermal energy stores of objects causing the temperature in to increase
What are optical fibres
Thing glass or plastic fibres that carry data (from telephones or computers) over long distances as pulses of visible light
How do optical fibres work
Because of reflection
The light rays are bounced back and forth until they reach the end of the fibre
What em wave are used in optical fibres
Visible light
What happens to the light as it travels along on the fibre
It isn’t easily absorbed or scattered
What is fluorescence
A property of certain chemicals where uv radiation is absorbed and them visible light is emitted
What do fluorescent lights generate
UV radiation which is absorbed and re emitted as visible light by a laye of a compound called a phosphor on the inside of a bulb
They are energy efficient so they’re good to use when light is needed for long periods
Security pens can be used to mark property with your name and what happens under uv light
The ink will glow fluorescent but otherwise it is invisible
This can help identify property if it is stolen
What can exposure to UV from the sun give u
A suntan
What do uv lamps give people
An artificial sun tan
Why can over exposure to uv be bad
Cause sun burn or skin cancer
What do radiographers in hospitals do
Take X-ray photographs of people to see if they have broken bones
How can X-rays give u an image
Pass easily through flesh but not easily through denser materials like metal or bone
So it is the amount of radiation absorbed or not absorbed that gives the image
How do radiographers use x rays and gamma rays to treat people with cancer
Through radiotherapy
High doses of these rays kill all living cells so are directed towards the cancer cells to avoid killing to many normal healthy cells
How can gamma rays be used as a medical tracer
Gamma emitting source is injected into the patient and its progress is followed around the body
Gamma radiation is well suited to this because it can pass our through the body to be detected
What do radiographers wear to protect themselfs from exposure
Lead aprons and stand behind lead screen or leave room
