Chapter 6h - 6m Flashcards
How does neon work?
When the neon atoms gain energy its electrons move to a higher orbit. When the fall back down they need to release the extra energy so it emits the extra energy as electromagnetic radiation which we see as visible lighty
What is radiation that causes electrons to escape called?
ionizing radiation
What is a tracer?
A radioactive substance that is deliberately injected into the body/moving water allows the movement of the substance to be followed by decking the ionizing radiation emitted
Describe one piece of evidence that supports Bohr’s idea of atoms having fixed orbits for electrons
What are some sources of background radiation?
radon gas
food and drink
cosmic rays
ground and buildings
medical treatment
How is radon gas created?
the radioactive gas is produced by rocks that contain small amounts of uranium
How is radon gas spread?
it diffuses into the air from rocks and soil and can build up in houses. especially when their is poor ventilation
How do we measure radioactivity?
photographic films
Geiger muller tube
What is a dosimeter and where is it used??
a dosimeter is a film badge which is used with people who work radiation in order to check how much radiation they have been exposed to
How does the Geiger muller tube work?
radiation passes through the tube ionizing gas inside it and allows as short pulse of current to flow. a GM tube can be connected to a counter which counts the pulses of current or the GM tube may give a clic keach time radiation is detected
What is the count rate?
the number of clicks per second or minute
Why do substances decay?
because the nucleus of a radioactive substance is unstable
What happens when decay occurs?
radiation is emitted which causes the nucleus to lose energy and become for stable
Can you predict when decay occurs?
You cant ,its a random proccess
Tell me information about alpha particle.(5)
They contain 2 protons and 2 neutrons making them have the same nucleus as a helium atom.
it has a charge of plus 2
it is very ionizing
it has afue centimeter travel distance in air
can be stopped by a sheet of paper
Tell me information Beta particle.(5)
mass is 1/1835
charge of -1
high speed electron
travels afue meters in air
moderately ionizing
can be stopped by 3mm think aluminum
Tell me information positrons.(3)
mass is 1/1835
charge of +!
high speed particle
travels a few meters in air
moderately ionizing
can be stopped by 3mm think aluminum
Tell me information Gamma rays.(5)
High frequency electromagnetic waves
speed of light
no charge
Few kilometer travel distance in air
weakly ionizing
needs several meters of concreate to be stopped
or thick lead
What happens to an element when it has an unstable nucleus and emits particles?
the atomic number can change. if this happenes the atom becomes a different element
What happens to an element when it emits a alpha particle?
the mass number goes down by 4
the atomic number goes down by 2
What happens to an element when it emits a beta particle?
the mass number does not change
the atomic number increases by 1
What happens to an element when it emits a positron particle?
the mass number does not change
the atomic number decreases by 1
What is another way a nucleus can lose energy?
gamma radiation, when the subatomic particles in the nucleus are rearranged
What is the activity of any radioactive substance?
the number of nuclear decays per second
How is the activity of a radioactive substance measured?
In becquerels (Bq)
What is the half-life of a radioactive substance?
The amount of time it takes for half the unstable nuclei in a sample of a radioactive isotope to decay.
How is the half-life measured?
how long it take for the activity to halve
What radiation is used to kill microorganisms?
gamma rays
How do you use radiation to detect leaks?
for example, a gamma source added to water is used to detect leaks in water pipes underground where there is a leak, water flows int other surrounding earth. a Geiger muller tube following the path of the pipe will detect higher levels of radiation where there is a leak
What is a tracer?
A radioactive substance that is deliberately injected into the body/moving water allows the movement of the substance to be followed by decking the ionizing radiation emitted
How do smoke alarms work?
smoke alarms contain a source of alpha particles, usually a radioactive isotope called americium-241. The detectors has an electrical circuit with an air gap between two electrically charged plates. the americium-241source release alpha particles, which ionize molecules in the air. These ions are attracted to plates with an opposite charge and so allow a small electrical current to flow
as long as this current is flowing, the alarm will not sound, when smoke gets into the gap the smoke particles slow down the ions,. this means that the current flowing across the gap decreases. the alarm sounds when the current drops below a certain level
How do we check the thickness of objects e.g. paper
Paper can be made in different thicknesses.
To check the thickness of the paper to see if its correct we use detectors, they count the rate at which beta particles get through the paper from a source on one side.
When the paper is too thin the amount of beta particles penetrate the paper and the detector records a higher count rate. a computer senses this and deduces that the force applied to make the paper is too strong so it makes it weaker to make the paper thicker, the opposite applies when the paper is too thick
What kind of damage is done when large amount of ionizing radiation is hitting the body?
Tissue damage - reddened skin
effects that cannot be seen
What kind of damage is done when small amount of ionizing radiation is hitting the body over a long period of time?
can damage inside the cell - mutation - cancer
What are some precautions that can be taken when handling radioactive sources and why do we take them?
use tong to increase distance between the people and the sources since intensity of radiation decreases with distance
storing them in lead-lined containers
What are some precautions taken in the hospital by medical staff?
increase distance
shielding
minimizing time spent
dosimeter badges
Why are sources with short half-lives used?
to minimize the time for which the patient is exposed
Why is being contaminated more dangerous than being irradiated?
you can move move away from the irradiating source while if you are contaminated the source is on you and it can only stop if the material decays or if it is removed which is rarely possible
Why are sources with longer half lives more dangerous in relevance to contamination?
they will stay longer on the body
How do you diagnose using gamma rays?
Tracers often contain a radioactive isotope attached to molecules that will be taken up by particular organs in the body. The tracer usually injected into the bloodstream, inhaled or directly injected into the organ the location of the tracer is the located by one or more cameras
How do you diagnose using positrons?
a tracer emits positrons. the positron meets a electron both it and the electron are destroys and two gamma rays are sent in opposite directions. The detector in a pet scanner moves around the patient, building up a set of images showing where different amount of gamma radiation are coming from
Why are radioactive sources with extremely short half life used in medical tracers?
so that other parts of the body are affected as little as possible
Why do the radioactive isotopes used in all medical tracers need to have as little half life as possible?
so that other parts of the body are affected as little as possible.
How does external radiotherapy work?
weak rays are sent from different direction with the center being the tumor, this is in order for the tumor to absorb a lot of energy while the surrounding area gets as little as possible
How do nuclear reactors work?
fuel rods - fission reactions - high speed- slowed down(moderator) - increases chance they are absorbed -control rods lower depending on how much you want fission reaction you want - control rods - using material that absorbs neutrons
What is electrostatic repulsion?
the repulsion of the positively charged nuclei
