chapter 13 - EM waves Flashcards
arrange the types of electromagnetic waves in increasing frequency
radio waves
microwaves
infrared radiation
visible light
ultraviolet radiation
x-rays
gamma rays
( rongzhu may incite violence upon Xtreme gaming )
state the waves that are red
radio waves
microwaves
infrared radiation
what colour is visible light?
all colours - ROYGBIV
state the waves that are violet
ultraviolet radiation
which wave has the lowest frequency?
radio waves
which wave has the shortest wavelength?
gamma rays
which wave has the highest frequency?
gamma rays
which wave has the longest wavelength?
radio waves
state the properties of electromagnetic waves
transverse waves
consist of electric fields and magnetic fields that oscillate 90°/perpendicularly to each other
they do not carry electric charge
can travel without a medium - at 30 x 10^8 in a vacuum
when it travels from one medium to another, its speed and wavelength change ; frequency does not change
they obey the laws of reflection and refraction
they transfer energy from one place to another
ionising waves are those with higher frequencies –> higher energies
state how ionising waves be harmful
ionising waves are those with higher frequencies and hence higher energies
they can eject electrons from atoms and molecules to create ions which in turn can cause harm by disrupting cell functions
applications of gamma rays
radiotherapy –> to kill cancer cells
example: gamma knife radio surgery
sterilizer –> for sterilisation of medical and laboratory equipment
industry radiography –> for checking of hidden defects
health effects of gamma rays
atoms/molecules of living cells are ionised leading to
- cell death/destruction/mutation
- abnormal cell division
which causes
leading to diseases and organ failure
applications of x-rays
x-ray imaging/CT scan in medical field –> for medical diagnosis
example: dental inspection, bone fractures
radiotherapy –> energetic X-rays used to kill cancer cells
industrial radiography –> for checking of manufacturing defects in METAL PARTS
x-ray screening –> for screening of baggage and luggage at airports for prohibited items
health effects of x-rays
causes cell destruction
causes mutation of normal cells leading to cancer and organ failure
application of ultraviolet rays
counterfeit detector machines using UV light –> for the detection of counterfeit money
sunbed –> for artificial tanning
germicidal lamps –> sterilisation of medical and laboratory equipment
health effects of ultraviolet rays
causes
- sunburn
- skin cancer
- premature ageing
applications of visible light
optical fibre –> endoscopy to illuminate internal organs
optical fibre –> bundled to form thicker undersea cables used to transmit large amount of data
health effects of visible light
causes blindness due to direct strong exposure on retina
applications of infrared waves
- hotter objects will emit more infrared radiation
intruder alarm system –> to detect the emitted infrared radiation to produce a thermal image
remote controller –> to control electrical devices
example: televisions, air conditioners
electric heaters –> electrically heated rods give out infrared radiation
applications of microwaves
*microwaves can penetrate the atmosphere, haze, clouds
microwave ovens –> penetrate into food to cause water molecules to vibrate vigorously, warming the food quickly
wifi signals –> used extensively for communication between devices like mobile phones or computers
satellite telecommunication –> to carry signals to and from satellites for satellite television / GPS (global positioning system) / mobile phone network
health effects of microwaves
microwave radiation can heat body tissues the same way it heats food
exposure to high levels of microwaves can cause skin burns or cataract=
application of radio waves
*radio waves are not used for satellite telecommunication
AM and FM radios –> for radio and television communication
RFID (radio frequency identification) tag –> used to tag merchandise in warehouses and shops
define ionisation
it is a physical process of converting an atom/molecule into an ion by addition or removal of charged particles (eg. electrons)
which EM waves are ionising?
gamma rays and x-rays (and higher frequency UV rays)
