P13 Electromagnetic waves Flashcards
RMIVUXG
is in order of what
order of highest to lowest wavelength
and lowest to highest energy and frequency
relationship between energy, frequency and wavelength of a wave
the higher the wavelength
the lower the energy and frequency
RMIVUXG =
radio waves
microwaves
infrared
visible light
ultraviolet
x rays
gamma
range wavelengths visible to humans
400nm to roughly 700nm
mgr do electromagnetic waves transfer and not transfer
transfer energy
not matter
what is white light
light containing all the colours of the visible light spectrum
how does infrared radiation affect skin cells?
- skin cells absorb infrared,
- which can damage, burn and kill them by heating them.
why do optical fibres often use infrared radiation rather than visible light?
it is absorbed less by the glass fibres than visible light
uses of radio waves
television and radio
uses of microwaves
heating food, satellite communications
how do microwaves heat food
- microwaves penetrate food,
- water molecules in the food absorb the microwaves, heating the food.
how can microwaves and radio waves be dangerous to humans?
dangerous as they penetrate people’s bodies
and heat their internal parts
what are carrier waves
how are they suited to their function
waves that carry any type of signal
they carry information by varying their amplitude
how does the length of a wave relate to:
- the amount of information it carries,
- its range,
- how much it spreads out.
the shorter the wave:
- the more information it carries,
- the shorter its range,
- the less it spreads out.
what doing optical fibres do
transmit signals carried by light or infrared radiation
how are optical fibres suited for their purpose:
- signals stay in the fibres because they reflect off the surfaces,
- carry lots of information due to short wavelength.
how can ultraviolet radiation be dangerous to humans
can cause:
- blindness,
- sunburn and skin cancer
differences between ultraviolet and x ray radiation
- x rays caused by electrons/particles moving at very high speeds being stopped
while gamma rays are caused by unstable nuclei releasing energy, - gamma rays have shorter wavelengths than x rays (so carry more information and transfer more energy).
how does the density of an object relate to how many X rays it absorbs
the denser an object
the more X rays it absorbs
2 uses of gamma rays
- killing harmful bacteria,
- killing cancer cells
2 examples of ionising radiation
X rays
gamma radiation
how to prevent harm from ultraviolet radiation
- wear skin creams,
- do not exceed the recommended time in sunbeds,
- wear goggles in sunbeds.
describe how X rays form a negative image
- X ray tube turns on and X rays are sent to body part,
- hard materials like bone and metal absorb X rays, making those areas light,
- X rays pass through soft materials like organs and tissues and reach the detector, making it dark,
- CCD converts X rays to light,
- light rays create electronic signals which display a digital image.
what is a contrast medium used for in X ray imaging?
to fill soft tissue so that it can absorb X rays
so that area will appear light and its internal surfaces visible on the digital image.
what is radiation dose a measure of?
a measure of the damage done to a person’s body due to ionising radiation
what does radiation does depend on?
- the type of radiation,
- how long one is exposed to the radiation,
- the amount of energy absorbed by the body per second.
unit of radiation dose
Sv
1Sv = 1000Sv
background sources of ionising radiation
cosmos radiation
radon gas
what are lead plates for in X ray imaging?
stop X rays reaching other parts of the body
compare the X rays used for imaging
with the X rays used for killing cancerous tumours
X rays for imaging are low energy as they are absorbed by bones but can pass through soft tissues and organs
X rays for killing cancerous tumours are higher energy as low energy would not be able to kill cancerous cells
uses of infrared radiation
optical fibres, infrared cameras, electrical heaters
uses of visible light
fibre optic communication
uses of ultraviolet
sunbeds, energy efficient lamps
