P4.3 Flashcards
List the different type of waves on the electromagnetic spectrum in order of frequency
Low-> high
Radio waves
Microwaves
Infrared
Visible light
Ultraviolet
X-rays
Gamma rays
What are the main features of a higher frequency wave
Higher frequency-> Higher energy of radiation
Makes higher frequency waves more:
Ionizing
Harmful to cell and tissue (cancers)
What are the main features of a lower frequency wave
Lower frequency -> lower energy of radiation
Used for communication
Less harmful for humans
What do all electromagnetic waves have in common?
Transverse waves
All together form a continuous spectrum
All em waves travel with the same speed in a vacuum
-> approximately the same in air
What is the speed of an em wave in a vacuum
About 3.0 x 10^8m /s
Describe the properties and uses of radio waves
Radio and television communication
>Its long wavelength+low frequency means it is less likely to be absorbed or scattered
>Can be reflected from the Earths atmosphere -> longer distance
Describe the properties and uses of microwaves
Satellite communication, telephones, WiFi
> Microwaves can penetrate the earths atmosphere
> Shorter wavelengths also carry more information and higher quality communication
Heating food:
> High intensity microwaves can heat things
Describe the properties and uses of infrared
heating/cooking things,electrical heaters
> Infrared emitted by warm objects
thermal imaging (medicine and research)/infrared cameras
>infrared emitted by warm objects
>can be detected using special camera
>used in research and medicine
Used in security cameras/motion sensors/night vision
>allow ‘night vision’
>infrared light illuminates area with beam without being seen
>when beam is disturbed -> camera detects -> alarm
Remote controls
>infrared LED send invisible signals to receiver on device
fiber optics communication
>infrared can undergo total internal reflection
>more efficient that visible light
Describe the properties and uses of visible light
Taking/seeing photographs
>cameras set up to detect visible light
Sometimes fiber optic communication
>can undergo total internal reflection
Only part of em spectrum human eye can see
Wavelengths from 750 (red) - 380 (violet) nanometers
Describe the properties and uses of ultraviolet
Detecting security ink/fluorescent bulbs
> fluorescence: some substances absorb+re-emit UV as visible light (glow)
Can cause skin disease
> suntan -> bodies protection against UV
> some ‘less harmful’ UV rays used in tanning beds
Describe the properties and uses of X-rays
Medicine
>X-ray able to pass through most tissue
>but absorbed by denser parts (ex: bones)
>leaves shadows -> seen using a detector or photographic film
Security checks/scanning luggage
Describe the properties and uses of gamma rays
VERY DANGEROUS
Kills cells + living tissue
Produced by radioactive material
Gene mutations and cancer
Cancer detection/treatment
>aimed and destroys cancerous cells
Sterilize food/medical equipment
>kills off bacteria
Why does higher frequency correlate to higher danger?
+ frequency = + ionizing = + danger
After visible light waves have enough energy to ionise atoms
Intensity also plays a key role is the amount of danger
What are the dangers associated with each em wave?
Radio -> no known danger
Micro -> possible heat damage to internal organs
Infrared -> skin burns
visible light -> bright light can cause eye damage
Ultraviolet -> eye damage, sunburn, skin cancer
X-rays -> kills cells, mutations, cancers
Gamma rays -> kills cells, mutations, cancers
How are microwaves dangerous to humans? How does this effect everyday life?
Certain frequencies of microwaves are absorbed by water molecules -> heat up
Humans = lots of water
> combined this can cause internal heating of organs
In everyday life:
Phones -> emit very little and do not cause any known harm
Microwaves ovens -> emit large amounts but are contained by metal walls
