P1.2 Flashcards
What are the seven types of electromagnetic waves?
Radio Waves Microwaves Infrared Visible Light Ultra Violet X-Rays Gamma rays
How do the waves change through the EM spectrum?
from radio to gamma
increase in frequency
decrease in wavelength
How is the EM spectrum dangerous?
increasing danger as frequency increases
at high frequency, most dangerous e.g gamma
low frequency generally safe e.g radio
What are the dangers of microwaves?
can heat cells inside the body and damage them
What are the dangers of infrared?
What makes it more dangerous than microwaves?
if exposed to it, can cause skin burns
higher frequency so higher heating effect as more easily absorbed
What are the dangers of Ultra Violet?
sunburn (surface skin cells damaged by absorbing UV rays in sunlight) can cause skin cancer
UV in sunlight can also cause eye damage
What are the dangers of X-Rays and Gamma Rays?
higher frequency so more dangerous than other EM waves
can cause cell mutation and damage which can lead to cancer
What are the uses of microwaves?
satellite communications
mobile phone signals
cooking (microwave ovens).
How are microwaves useful for satellite communications?
signal from transmitter sent into space and picked up by satellite receiver dish above Earth
satellite transmits signal back to Earth, received by satellite dish on ground
small time delay between being sent and received as large distance
How do microwave ovens use microwaves?
microwave energy absorbed by water molecules in food, heats them up and cooks the food
How are microwaves used for mobile phone signals?
signals travel as microwaves to nearest transmitter
What are the uses of radio waves?
How do they work?
broadcast tv and radio signals
transmitting satellite signals
very short waves pass through Earth’s atmosphere , used for satellite communications
short waves travel long distances, reflect off Earth’s atmosphere
long wave radio waves sent and received half way around world. bend round curved surface of Earth
tb and fm radio - in line of sight of transmitter
What are uses for infrared?
thermal imaging - e.g night vision cameras
turns it into electrical signal which is displayed as image on screen
monitor temperatures e.g heat loss through uninsulated roof
optical fibres - use infrared to carry data over long distances. work by bouncing waves off sides of inner core of glass/plastic
cooking e.g grills and toasters
remote controls - use infrared to transfer info to tvs and dvd players
transmit info between mobiles and computers over short distances
security systems - e.g burglar alarms and security lights. sensors detect heat from intruder’s body
How is ultraviolet used?
detect forgeries - banks print markings in fluorescent ink on bank notes. under uv light, genuine notes display markings as markings absorb UV light. fake don’t show markings as printed on cheaper paper and glow all over
fluorescent lamps use Uv radiation to emit visible light (safe as Uv absorbed by phosphor coating on inside of glass)
security pens - can mark property with the ink. only visible under uV light, can help police find propery if stolen
disinfect water - UV kills viruses and bacteria
How are X-Rays used?
radiographers - hopsitals use to check for broken bones. x-rays pass easily through flesh but not bones. x-ray image given based on amount of radiation absorbed
airport security - use to scan luggage and check for suspicious looking objects
some airports use xray scanners on passengers to check for concealed weapons or explosives (low level so not as harmful as ones in hospitals)
How do radiographers in hospitals protect themselves from x-rays?
wear lead aprons
stand behind lead screen or leave room
keeps exposure minimum
How is visible light useful?
only see objects when illuminated and give out/reflect light
when light enters eye, refracted through lens
focused onto retina at back of eye. retina sends message to brain via optic nerve
brain interprets them
How is visible light used in photography?
camera uses lens to focus visible light onto light sensitive film or electronic sensor that records image
lens aperture controls amount of light entering camera. shutter speed determines how long film/sensor exposed to light
by varying these, photographers can capture as much/little light as they want in the photo
How are gamma rays used in radiotherapy?
high doses kill all living cells so can be used to treat cancer
directed carefully and at right dosage to kill cancer cells while killing as few normal cells as possible
some damage to normal cells, patient feels ill
How can gamma rays be used to detect cancer?
radioactive isotope injected into patient
gamma camera used to detect where isotope is in body
creates image that can be used to detect where there may be cancer
How can gamma rays be used in sterilisation?
food exposed to high doses, kills microbes and keeps food fresh for longer
medical equipment sterilised in same way instead of boiling
advantage of using irradiation instead of boiling is not high temperatures- so plastic equipment/apples etc can be sterilised without being damaged
What is ionising radiation and how does it work?
3 types - alpha,beta,gamma
emitted by radioactive sources when their nuclei decay
random can’t predict- when happens source will spit one of 3 types
all transfer energy - called ionising as energetic so bash into atoms, knocking electrons off them
How is ionising radiation dangerous?
all have own uses but can be dangerous
if radiation enters body, it will collide with molecules in cells and cause ionisation
this ionisation will damage and destroy the molecules and lead to cancer
