Physics - Electromagnetic Waves + More Flashcards
What 4 things are electromagnetic waves?
- ? waves that can travel through a ?
- consist of vibrating and ? field
- travel at same ? in a vacuum, ? m/s
- Transfer ? from a source until ?
transverse, vaccum,
magnetic,
speed, 300,000,000,
energy, absorbed
on the visible spectrum where is the wavelength highest?
red
on the visible spectrum where is the frequency highest?
violet
atomic changes lead to electromagnetic waves being produced , give two examples of this:
-arrangement of electrons
- radioactive nuclei decay giving off particles, and a subsequent release of energy in the form of a gamma
Radio waves production -
are made by oscillating ?, these currents flow in the ? aerial, which cause oscillating electric and ? fields to be created - an ? field
electrons, transmitting, magnetic, electromagnetic
What are radio waves used in?
comma - radio and TV signals as well as satellite comms
what are the 3 different types of radio waves and what are their lengths they can travel
long - (10-20km), short/medium (1-10km), FM and TV (10cm -10m)
Satellite comms - what does their long wavelength enable them to do?
pass through the earths atmosphere without being refracted or absorbed
how do microwaves work?
water molecules absorb the ? in the microwave ? - then transferring the ? energy to the thermal ? store of the food
micro waves, oven, waves’, energy
what is a black body?
an object that absorbs all the radiation it receives and emits all types of radiation
what does a blackbody not do?
transmit or reflect any radiation/wavelengths of light
what do hotter bodies have?
greater amount of radiation per second
greater amount of short wave radiation released
As temperature increases in a blackbody what happens?
the intensity of every ? wavelength increased, the ? the wavelength the more rapid the ? in intensity, the peak ? occurs at ? wavelength
emitted, shorter, rise, intensity, shorter
why are all objects continuously emitting electromagnetic radiation?
due to the energy in their thermal stores
the radiation is of a ? range of wavelengths across the ? spectrum. the amount of type/? of radiation depends on the object’s?
wide, electromagnetic, intensity, temperature
which type of electromagnetic wave has the highest intensity?
visible light
electromagnetic spectrum going from longest wavelengths to highest frequency
radio waves —> microwaves —> infrared —> visible light —> ultraviolet —> x-ray —> gamma ray
definition of reflection
change in direction of a wavefront between 2 different media (plural of medium)
what is speculation reflection - what surface and reflection?
a smooth surface and single/normal reflection
what is diffuse reflection - what surface and type of reflection?
rough surface, and causes scattering
definition of absorption
process in which light is transferred to energy within a material
definition of transmission?
when light passes through a material without being reflected or absorbed
definition of opaque?
a material that does not transmit light (but does absorb and reflect it)
definition of transparent??
a material that allows light to pass through without being scattered, eg : a window
definition of translucent?
a material that allows light to pass through but with (some) scattering, eg: plastic
What is Beta - decay??
When a neutron turns into a proton which emits an electron and an antineutrino (the antimatter form of a neutrino)
What is alpha decay?
A particle composed of 2 protons and 2 neutrons are emitted
What is Beta + decay?
causes the atomic no if the nucleus to increase by one while the mass number stays the same
What is a half-life?
the time it takes for the radioactivity of a particle to half (decrease by half)
microwaves?, uses and dangers
used to warm food, and sending signals to and from satellites and antennas, good to transmit info from one place to another through any type of weather/ precipitation, dangers : can heat up body tissues and endanger people
infrared?, uses and dangers
can penetrate air, but not most solids besides glass, used for night vision, security systems and remote controls
ultraviolet?, uses and dangers
can’t pass through most solid materials , but can air (apart from ozone layer), can be used for sun beds, detecting forged bank notes and security coding - due to fluorescent ink + dangers include - skin cancer layer on and too much uv light can damage retina
x-rays?, uses and dangers
pass through tissue, but not bone - bone shows up and tissue is transparent forming on image, are a type of ionising radiation, dangers - can damage cells and result in cancer
gamma rays?, uses and dangers
some radioactive materials emit them, can pass straight through body, can be used to treat cancer, sterilise medical equipment and food, as they kill living cells eg bacteria or mould, dangers - high intensity can kill living cells leading to cancer
wavelength of radio waves?
10 to the 4 to 10 to the -1 (around a couple km to a few cm)
wavelength of microwaves
around 10 to the -2 (0.1 - 10cm)
wavelength of infrared?
around 10 to the 15 ( 0.0007-0.003mm)
visible light wavelength?
around 10 to the -7
UV wavelength?
around 10 to the -8, (0.00001 - 0.0004)
wavelength of x-rays?
10 to the -10
wavelength of gamma rays?
10 to the -15
typical radius of an atom?
1 * 10 to the -10 m
how many times smaller than an atom is the typicak radius of the nucleus?
10,000 times smaller
where is almost most of the mass concentrated in an atom??
the nucleus!
what is a beta particle?
a high speed electron ejected from the nucleus
What is ionising radiation?
Any type of ? - particles or ? waves that can pass through ? and dislodge electrons from ? causing them to ? ions
radiation, electromagnetic, matter, atoms, become
Too much ionising radiation can lead to what?
Cell damage, which can lead to mutations and then cancer (as well as possible cell death)
What do unstable atomic nuclei give out and what is this process called?
Ionising radiation - they change to become more stable, this is called nucleur decay
Nucleur decay is a random process - what does this mean?
You can’t predict when the ionising radiation is going to happen and in what way?
there are no nuclei with an atomic number greater than ? - unstable nuckei with high ? numbers usually ? by this
82, atomic, decay
History of the atom? Order in terms of names
Democritus, John Dalton, JJ Thomson, Ernest Rutherford, Niels Bohr, James Chadwick
History of the atom? Order in terms of dates
c.400BCE, 1826, 1897, 1905, 1913, 1932
History of the atom? Order in terms of what was discovered
400 BCE - every substance is made of small indivisible particles
1826 - matter is made from a finite set of atoms
1897 - plum pudding model - negatively charged plums (electrons) embedded in a positively charged pudding (nucleus)
1905 - atoms are mostly empty space, positive charge in a small dense nucleus and is orbited by electrons
1913 - electrons orbit nucleus at different diameters/energy levels
1932 - are also neutrons in the nucleus which have no charge (neutral particles)
What is activity (to do with atoms)
The number of decays per second - measured in bequerels (Bq)
What is count rate?
Number of decays detected per second - measure in counts per second
How are count rate and activity related?
They are proportional to one another - but the count rate is always less than the activity because not every radioactive decay is detected!
natural sources of background radiation in order of preference? (2 examples)
- Radon from rock/ground
- Rocks and building materials
artificial sources of background radiation in order of preference?
a named medical source, eg : X-ray, CT scan, radiotherapy
a naked nuclear source, eg: nuclear power stations, nuclear weapons testing, nuclear accidents
what is contamination?
the unwanted presence of materials containing radioactive atoms on or in other materials
What is irradiation?
the process of exposing a material to ionising radiation - does NOT make a material radioactive
how does contamination occur?
when a radioactive ? gets somewhere it shouldn’t ?, eg after a nuclear ? , small amount of this isotope will emit ?, making the material ?
isotope, be, accident, radiation, radioactive
danger of contamination and how it can be prevented? :
danger of ? can lead to prolonged ? , however this can be prevented by wearing disposable gloves and ? and removing soil from around ?
contamination, irradiation, clothes, Fukushima
what is radiation measured in? (two answers)
sieverts and usually millisivierts (mSv)
how can you prevent risk of irradiation and why is this important?
can prevent this by ?, eg placing an absorber between the ? of ionising ?, this is important as exposure can cause the ? of DNA in cells, which can cause either cancer or cell ? (in high doses)
shielding, source, radiation, mutation death
where is carbon 14 produced and what is its half life?
in the upper atmosphere, (is an isotope of carbon), and has a half life of 5740 years
what ratio of carbon atoms is constant in the atmosphere?
C14 : C12
why does the C14:C12 ratio decrease as an organism dies?
as the C14 decays but is no longer replaced
how do people use the ratio of C14 : C12 in real life?
they compare the ratio of dead organic material to living organic material to give an estimate for the age of the material
3 types of medical uses of radiation
- Tracers
- treatment with implanted sources (internal radiotherapy)
- external radiotherapy, x rays and CT scans
ionising radiation has a small probability of causing damage to the human body but is still only used in two circumstances :
when probability is negligible (eg radiation dose from x ray compared to background dose from radon), or when benefits outweigh risk like in radiotherapy
Tracers - what happens?
A patient is injected with a ?, that concentrates where there is damage in the ?, this radiation is ? outside of the body
radioisotope, body, detected
Internal radiotherapy - what happens?
a radioactive source is implanted where the cells need to be killed
External radiation- what happens?
When a source of ? is rotated around the ? and the body is exposed at ? angles, so tissues receive high enough ? to cause cell ?
radiation, body, different, dosages, death
what type of rays do tracers use and why?
gamma rays - they don’t irradiate surrounding tissues as much as the other two but are still penetrating
Difference between alpha beta and gamma for their charge/ what they are?
Alpha - positively charged, beta - a form of electron, gamma - an electromagnetic wave
why does internal radiotherapy use beta radiation?
as it needs to be penetrating enough to travel a small distance
Difference between alpha and beta radiation?
- Alpha has high power ionisation, while beta has low power ionisation
- Alpha has low penetration, while beta has high penetration
what is a gamma ray?
a low ionising, highly penetrative wave like radiation
What type of radiation does external radiation radiation use and why doesn’t it have a half life?
High energy x rays - high penetration to pass through body to target tissues and it has no half life as the x rays are only produced during treatment so patient is only irradiated throughout
tracer’s half life and why?
a few hours to give time to be detected but not contaminate patient too much
half life of internal radiotherapy?
a few hours/ days, as it’s long enough to cause cell death but prevents any extra irradiation
What is nuclear fission?
Splitting of an atomic nucleus to form two smaller nuclei and realising energy
Fission is an alternative way very unstable nuclei with high atomic numbers can do what?
Become stable, but spontaneous nuclear fission is very very rare
What uses induced nuclear fission?
Nuclear power stations
To induce nuclear ? inside a ? reactor, a neutron needs to be ? by the nucleus of the nuclear fuel (? 235 or plutonium ? ) . This newly formed nucleus then ? into 2 smaller ?
fission, nuclear, absorbed, Uranium, 239, fissions, nuclei
- a thermal ? is absorbed by a uranium ? nucleus so that it becomes ? 236
- uranium 236 ? (the ? nucleus) fissions to produce two smaller ? nuclei, during the fission process, ? is released along with 2 or ? neutrons which go on to cause further ? - a chain ?
- neutron, 235, uranium
- nucleus, parent, daughter, energy, 3, fissions, reaction
difference between controlled and uncontrolled chain reactions?
uncontrolled - nearly all neutrons released cause further fissions, but controlled - is when only one neutrons goes on to be absorbed by a fuel nucleus which produces steady energy (in a nuclear power station)
the daughter nuclei are released with ? kinetic energies, and the 2 neutrons are ? with high ? energies, however the neutrons move a lot ? than the nuclei due to their low ? - Ek = mv (?)
large, released, kinetic, faster, mass, squared
How does controlled chain reactions work?
the neutrons are ? down and moderated to become ? neutrons - which can be done by using a ? and the excess ? produced by each ? are absorbed by ? rods
slowed, thermal, moderator, neutrons, fission, control
why is there a mass defect?
because the mass of the parent nucleus is always bigger than the mass of the products, and the missing mass is this where it is released through energy
what does the moderator do?
slows down neutrons
what does the moderator do?
slows down neutrons
what does a control rod do?
absorbs excess neutrons
what does shielding do?
to shield surroundings from ionising radiations
3 key pros of nuclear power stations
lots of fuel, reliable energy source, no greenhouse gases
3 cons of nuclear power stations?
threats of nuclear accidents, not renewable energy source, storage of nuclear waste
examples of low level nuclear waste?
disposable clothing that may be contaminated
medium level nuclear waste eg:
reactor components and effluents
examples of high level nuclear waste?
spent fuel rods
what are fuel rods?
where the fuel is put into in nuclear power stations
why does all nuclear waste have to be stored for such a long time?
still very radioactive - will remain hazardous for centuries
Definition of nuclear fusion?
The joining of two light nuclei to form a larger, heavier nucleus and releasing energy
How many tonnes of hydrogen does the sun fuse into helium every second?
620M
Nuclear fusion requires very high ?, and we don’t have materials that can ? this, and as well as this nuclear ? is also ? hard to do
temperatures, withstand, fusion, very
what are the 3 isotopes of hydrogen?
protium, deuterium and tritium
how many electrons and protons and neutrons does protium have (and what is its mass number)
1 electron, 1 proton, and no neutrons and the mass number is 1
how many electrons and protons and neutrons does deuterium have (and what is its mass number)
1 electron, 1 proton and 1 neutron - so a mass number of 2
how many electrons and protons and neutrons does tritium have (and what is its mass number)
1 electron, 1 proton, and 2 neutrons - so a mass number of 3
what is alpha radiation used in and what is an alpha particle?
smoke alarms, and they are made from a helium nucleus
what is beta radiation used in?
quality control in manufacturing
alpha particles cannot go through what?
paper/skin
beta particles cannot go through what but can go through..?
aluminium, but can go through skin/paper
gamma rays cannot go through what but can go through..?
aluminium and paper/skin but not through lead
a neutron cannot go through what but can go through..?
can’t go through concrete, but can go through lead, aluminium, and paper/skin
what does alpha decay do to the atomic and mass number?
decreases the mass number by 4, and the atomic number by 2
what does beta decay do to the atomic and mass number?
increases atomic number by 1 (and the mass number by 0)
