EM Waves and Their Uses Flashcards
What two categories do microwaves spilt into
those absorbed by water molecules and those not absorbed by water molecules
Example of microwaves that aren’t absorbed by water molecules
microwaves
How do microwaves that aren’t absorbed by water molecules transfer signals
they have to pass through the earth’s atmosphere. They are then received by satellites and then they are transmitted back to earth
How do microwaves that are absorbed by water molecules transfer signals
when microwaves are fired at the food, the energy from the waves gets absorbed by the water molecules. The molecules then start to vibrate with the new energy and some of the energy spread to other molecules until the food is heated up
Where is IR energy emitted from
All energy that has thermal energy
Example of IR waves
infrared cameras that see in the dark
True or false
the hotter the organism to the darker the colour of the infrared wave
False. the brighter the colour
How is infrared used in cooking
By heating up the metal bar in ovens, It emits lots of infrared radiation and this heats up the food
How is infrared used in heaters?
By heating up the metal bar, it emits lots of infrared radiation and it gets transferred to the surroundings
How dangerous are infrared are microwaves
They are only harmful in high quantities
What do we use visible light to do
see idiffrent colours and comunicste
What are optical fibers`
thin glass/ plastic fibers that can transmit forces of light over long distances. The light bounces back and forth until it gets to the end of the beam. You have to use materials that will totally reflect light
What is the alternative for optical fibers?
Electrical copper wires
What is Ultraviolet
waves that come from the sun
how do we use ultraviolet
as things like sunbeds, security pens
What is fluorescence
ultraviolet is absorbed then reemitted as visible light
How do fluorescent lights work
they generate UV radiation which is absorbed by a layer of phosphor and re-emits the energy as visible lights. These are energy efficient
What do x-rays do
view the external structure of objects
How do x-rays work
firing x-rays through a person’s body. It will get absorbed by the bones and some will last through the parts that are mostly air e.g lungs, intestines and will only partially pass through the heart
What are gamma rays used for
sterilization, cures for cancer
Why are gamma rays used for sterilizing medical equipment instead of hot water?
They can kill microorganisms without damaging the equipment. Boiling water can’t be used for stuff like plastic
How can gamma rays sterilize food
It kills all the microorganisms without damaging the food and it is still safe to eat
The trade-off for gamma and x-rays
they are ionising radiation so they can damage our cells
ut they are worth the risk
