Electromagnetic Waves Flashcards
What types of waves are em waves
Transverse waves that transfer energy from a source to an absorber
How do em waves travel and through what can they travel
They travel at the same speed as vibrations of electric and magnetic fields
Through air or a vacuum
What are the 7 types em waves are grouped
Radio waves Microwaves Infra red Visible light Ultra violet X-rays Gamma rays Roman Men Invented Very Unusual X-ray Guns
How is the em spectrum ordered from radio waves to gamma rays
It increases in frequency
It decreases in wavelength
Why is there such a merge change in frequencies
Em waves are generated by a variety of changes in the atoms and their nuclei
What currents are in electromagnetic wave s
Alternating currents as they are made up of oscillating charges and produce oscillating electric and magnetic fields
How do you produce radio waves and what is the object called
Use an alternating current in a circuit
A transmitter makes charges oscillate to create a radio wave
What happens to radio waves when they reach the receiver and to the electrons in the material of the receiver
The wave is absorbed and the energy is transferred to the electrons in the material of the receiver
This energy causes the electrons to oscillate and if the receiver is apart of a complete circuit it will generate an alternating current
How long are radio waves wavelengths
Longer than 10cm
1m - 10*4 m
How can long wave radio waves get around the world and over mountains
The wavelengths diffract around the curved surface of the earth and over mountains
How are short wave radio waves still received at long distances from the transmitter
They are reflected from the ionosphere
What’s the ionosphere
An electrically charged layer of the earths upper atmosphere
What are the wavelengths of the radiowaves for tv and fm radio transmissions
They are very short wavelengths so you must be insight of a transmitter
What waves are used for communication too and from satellites
Microwaves
How are the wavelengths in microwave ovens and microwaves to satellites different
In microwaves oven the waves need to be absorbed by water molecules in food so they use a different wavelength
What happens to the microwaves in microwave ovens
The microwaves penetrate up to a few cm in the food before being absorbed by the water molecules in the food and thy here transfer the energy they are carrying to heat up the water which passes heat through the rest of the food
What are Infared cameras used for and how is this done
To detect infared radiation and monitor temperature
The camera detects ir radiation and turns it into an electrical signal to display on a screen
The hotter the object the brighter it appears
What can Infared radiation be used for
Detecting or increasing temperature
How does Infared radiation increase temperature
When an object absorbs IR radiation
Eg when cooking food
How do electric heaters work
They contain a long piece of wire that heats up when a current flows through it
The wire will emit a lot of Infared radiation which will be absorbed by other objects and the air
What are optical fibres
Thin glass or plastic fibres that can carry data over long distances as pulses of visible light
How do fibre optic cables work
Through reflection
The light rays are bounced back and forth until the reach the end of the fibre
The light is not easily absorbed as it travels
How are flourescent colours so bright
Fluorescence is a property of a certain chemical which absorbs ultraviolet and Emmits visible light
Where’s is ultraviolet radiation used
Flourescent lights
Security pens
Suntans
What waves are used in medicine
X-rays and gamma rays
How do X-rays work to look at bones
The X-ray will easily pass though the flesh but both through the denser material of bones
So the amount of radiation that’s absorbed gives the the X-ray image
How do radiographer uses X-rays and gamma rays to treat cancer
High doses of the waves can kill cancer cells
How is gamma radiation used as a medical tracer
A gamma emmiting source is objected into a patient and followed around the body
What waves and types can cause damage when passing though the body
Waves with high frequency like gamma X-rays and UV
As they transfer lots of energy
How is UV radiation damaging
It damages surface cells and lead to sunburn
More seriously it can lead to skin cancer
What can too much exposure to X-rays and gamma rays cause
Ionising radiation where the energy kicks off electrons in atoms
This causes gene mutation or cell destruction and cancer
What is radiation dose
And what is it measured in
Measured in sieverts
Is a measure of the risk of harm of a body being exposed to radiation
Depends on total amount of radiation absorbed and how harmful the type of radiation is
