The ElectroMagnetic Spectrum Flashcards
What is the electro magnetic spectrum in order of wavelength longest to shortest
Radio Micro Infra red Visible Ultra X-ray Gamma
How was infrared discovered
By Hershel in 1800
He split up light into a spectrum through a prism
He wanted to look at the heat of the colours so measured each colour and saw that red was the warmest
He measured beyond red and saw that this was the hottest so this proved there was light beyond visible
How was ultraviolet discovered
Ritter knew that silver chloride turned from white to black when exposed to light
He spilt up a spectrum and tested on each colour
He timed how long it took each picture to turn black
The violet end was longest so he tested beyond violet and this took longer still so there was radiation beyond the violet end
What effects do microwaves have on people
They have a similar frequency to the vibrations of molecules so increase the vibrations resulting in heating
They can heat human body cells
So when mobiles are held close to the brain they could be heating human cells causing tumours
How does infrared effect people
They can vibrate surface molecules which heats the cells
It carries more energy than micro waves so can cause Nasty skin burns
What effect does ultraviolet have in people
It has more energy and a higher frequency than infrared
It is ionising so can knock electrons off atoms
It causes sunburn which can lead to cell mutations causing skin cancer
Can also cause eye damage
What effect does gamma/X-rays have on people
They are very ionising
They can cause cell mutation or destruction anywhere in the body which can lead to cancer or tissue damage
What are the buses of radio waves
Used to broadcast tv and radio signals and transmit satalite signals
some have long wave lengths so can bend around the earth and travel long distances
Others have very short wavelengths meaning they can only be received when in direct sight of the transmitter
Waves with medium wavelengths can be detected at long distances because they can reflect off of the ionosphere
What are the uses of microwaves
They can pass easily through the atmosphere so are used for communication to satellites
For satellite tv a signal from a transmitter is transmitted into space and then transmitted back to the earth in a different direction where its detected by a satellite dish on the ground so there’s a slight delay
This is also used for mobile phones
How do microwave ovens work
The micro waves are different wavelengths used to the ones in communications so they’re absorbed by the water molecules in the food
The energy from the absorbed microwaves causes the food to heat and the heat is converted or conducted to other parts of the food
What is infrared radiation used for
It’s given out by hot objects so can be used to monitor hot objects
Heat loss through a roof can be detected by IR detectors
It’s detected by night vision equipment which turns it into an electrical signal and displays it on a screen the brighter the image the more radiation
Optical fibres reflect pulses of infrared off their core to transmit data over long distances
What are the uses of infrared in the home
Cooking eg grills and toasters
Remote controls
Transmitting information between phones and computers only over short distances
Sensors are used in security systems and detect heat from the intruders body
What are the uses of visible light
When light enters the eye it is refracted then focused onto the retina then the brain interprets the picture
Photography works in the same way
The shutter speed determines how long the film or sensor is exposed to light
Changing the shutter speed allows the photographer to decide how much light to use
What are the uses of ultraviolet
When uv is absorbed and visible light is emitted it causes fluorescence
Banks print special markings in special ink on bank notes
Under a uv light genuine bank notes show the fluorescent markings
Fluorescent lamps use uv radiation to emit visible light
Security pens can mark property in ink that is only visible in uv light
It can be used to disinfect water by killing off any viruses and bacteria in the water
What are the uses of X-rays
Radiographers in hospitals take X-ray photographs of people to see if they have broken bones
They pass easily through flesh but are absorbed by denser materials so the amount of radiation absorbed gives you an image
X rays can cause cancer so the radiographer wear lead aprons stand behind a lead screen or leave the room
Airport security can uses X-rays to scan luggage or look for concealed weapons
