EM Waves Flashcards
What sort of waves are EM waves
EM waves are waves that transfer energy from a source to an absorber
All EM waves are transverse waves
What sort of matter can EM waves travel through
-EM waves can travel through both air and a vacuum such as space. They travel at the same speed through all matter
What are the different waves in the EM spectrum
- red meat is very unhealthy Xept for giraffe
- Radiowaves
- Microwaves
- Infrared waves
- Visible light
- UV waves
- Gamma waves
What happens to wavelength and frequency as you go down the EM spectrum
As you go down the EM spectrum EM waves increase in frequency but decrease in wavelength
Why can long wavelength radiowaves be transmitted over long distances
Long wavelength radiowaves can be transmitted over large distance because they can diffract (bend) over curved parts of the earth
Why can short wavelength radiowaves also be used over long distances
Short wavelength radiowaves can also be used over long distances as they are reflected off the ionsphere(the electrically charged part of the atmosphere )
What sort of wavelengths of radiowaves are used for bluetooth
For bluetooth short wavelengths are used to send data over short distances
What can microwaves be used for
Microwaves can be used for comminucations.They are sent through the earths atmosphere to a satellite dish which transmits the signal back in a different direction. This signal is recieved by satellite on the ground .
How do microwaves heat up food
Microwaves are absorbed by water molecules in the food. They transfer their energy to the water molecules that then heat up. This heat is then transferred to the rest of the food molecules causing the rest of the food to heat up
What can Infrared radiation be used for
Infrared radiation can be used for
- Thermal imaging cameras-this is where a camera detects the IR radiation emmited by an object and turns it into an electrical signal which is then displayed on a screen as a picture. The hotter the object is , the brighter it appears
- Electical heaters(emit IR radiation which causes air and objects in the room to heat up)
- Security systems
- Heating food
- Short length communications
What can light be used for
Light can be used for optical fibres(pulses of light carry data along cables by reflecting of cable), it can be also used for photography.
What can UV radiation be used for
UV radiation can be used for security pens as when UV light is shone on the ink it emmits visble light and can also be used in tanning salons to produce tan.
Over exposure to UV radiation can cause skin cancer and cause your skin to age prematurley
How are X rays used in medical imaging
X rays are used in medical imaginh as they pass easily through flesh and not so easily through denser material such as metal and bones. The amount of radiation that is absorbed or not absorbed (if bones are there) gives an image of where bones are .
What are gamma rays used as
Gamma rays are used in medical imaging. A gamma emmiting source is placed in the body and its progress is followed around the body.
What are the dangers of radiation
- Low frequency waves dont transfer alot of energy so can be transferred through tissue without being absorbed
- UV rays cause damage to the surface of cells . This can cause sunburn and the skin to age prematurley. This can also cause skin cancer and blindness
- X rays and Gamma rays are ionising types of radiation. They knock electrons off atoms when absorbed. This can lead to gene mutations and cancer
