The Electromagnetic Spectrum Flashcards
What are the seven types of wave in order of wavelength from longest to shortest
Radio waves Micro waves Infra red Visible Ultraviolet X-rays Gamma rays
Describe how infra red was discovered
By Hershel the temperature in the different colours and beyond red was the warmest
Describe how ultraviolet was discovered
By Ritter silver chloride reacted fasted beyond the violet end of the spectrum
Describe the properties of em waves
Waves nearer to the ends can usually pass through things whereas waves closer to the middle are often absorbed
The higher the frequency the more energy therefor the more harmful the wave
Describe the dangers of microwaves
Similar frequency to the vibrations of many molecules so they increase the vibrations causing heating
Microwaves can heat human body cells
Describe the dangers of infra red radiation
They can make surface molecules vibrate so have a heating effect but it has a higher frequency so more energy it can cause nasty skin burns
Describe the dangers of ultraviolet radiation
It is ionising so can knock electrons off atoms this causes sun burn it can also lead to cell mutation or destruction and ultimately skin cancer or eye damage
Describe the dangers of gamma rays
Very high frequency waves such as gamma and X-rays they are ionising and have lots of energy they can cause cell mutation or destruction leading to tissue damage or cancer
Describe the uses of radio waves
Used to broadcast radio tv and radio and transmit data lite signals
Long wavelengths can travel long distances and can bend around surfaces
Radio waves used for tv and fm radio have short wavelengths must be in direct sight of the transmitter
Short wave radio signals can be received at long distances because they are reflected from the ionosphere some very short wavelengths can pass through the ionosphere and are used for satellites
Describe the uses of microwaves
Communications to and from satellites use microwaves
Also the mobile phone signals move too and from the transmitters using micro waves
Describe how microwaves are used in a microwave oven
The microwaves are absorbed by the water molecules to heat it up so they need to be different wavelengths the energy goes a few centimetres into the food before they are absorbed then the energy heats up the food
Describe how infrared radiation is used
It is given out by all hot objects therefore infra red sensors use infrared to monitor heat loss
It can also be used in night vision cameras the hotter the object the brighter it glows with infra red waves
Cooking eg grills and toasters
Remote controls
To transmit information I’ve short distances e.g. Mobile phone to laptop
Infrared sensors can be used in burglar alarms
Describe optical fibres
They use infra red to transmit information over long distances in wires they work by bouncing the waves of the inside of the fibre until it reaches the end
What are the uses of ultraviolet radiation
Fluorescence is a property of certain chemicals when uv radiation is absorbed and then visible light is emitted
Banks print money with florescent Ink on them so by shining a uv light at them fake ones can be detected
Fluorescent lamps emit uv radiation
Fluorescent ink can be put on property so if it is stolen the police can use uv light to identify it
It can be used to disinfect water
How are x rays used
They pass easily through flesh but not bone so the amount of radiation absorbed or not absorbed gives us an X-ray image
X rays can cause cancer so the X-ray doctor will wear a lead apron and leave the room when exposed to X-rays
Airport security can use X-rays to look for suspicious objects in luggage or weapons on people but they are less harmful that the hospital ones
