What is ultrasound?
- sound with a high frequency than we can not hear
- above 20,000 Hz
What are compressions?
-parts of a wave under high pressure (lots of particles)
What is sound?
-a longitudinal wave
How is ultrasound used to get rid of kidney stones and why is it useful??
- ultrasound beam concentrates high energy waves at the kidney stone and breaks it down into sand-like particles
- particles pass out of body in urine
- useful because patient doesn’t need surgery and it is relatively painless
What are some uses of ultrasound?
- breaking down accumulations in the body
- scanning the body
How is ultrasound used for body scans?
- ultrasound waves pass through the body, but when waves reach a boundary between different media (like fluid in the womb and the skin of foetus) some of the wave is reflected back and detected, returning back from different lengths at different
- exact timing and distribution of these echoes are processed by a computer to produce video image of whatever is being scanned
What advantages does ultrasound have over x-rays?
- x-rays pass easily through soft tissue like muscle and skin, so you can only use them to make images of hard things like bone. Ultrasound is great for imaging soft tissue
- ultrasound is very safe
Describe the properties of beta radiation.
- fast-moving electron
- virtually no mass
- charge of -1
Describe the properties of alpha radiation.
- helium nucleus
- mass of 4
- charge of +2
- made of two protons and two neutrons
What are radioactive materials made from and how do they work?
- made of atoms with unstable nuclei that natually decay at random
- as atoms decay they give out alpha, beta and gamma
- during the decay, the nucleus often changes into a new element
What is half-life?
What is a short and long half-life?
- time taken for half of the radioactive nuclei now present to decay
- short half-life means activity falls quickly, because lots of nuclei decay in a short time
- long half-life means activity falls slowly, because most of the nuclei don’t decay for a long time
How does radioactivity decrease?
- each time an unstable nucleus decays and emits radiation, one more radioactive nucleus isn’t there to decay later
- as more unstable nuclei decay, radioactivity of a source as a whole decreases (the older the source, the less radiations emitted)
- how quickly the activity decrease varies a lot
What are rarefractions?
-parts of a wave under low pressure (fewer particles)
What happens when a nucleus emits an alpha particle?
- mass number decreases by 4 (because it loses two protons and two neutrons)
- atomic number decreases by 2 (because it has too less protons)
- forms a new element (because the number of protons have changed)
What happens when a nucleus emits a beta particle?
- mass number doesn’t change (because it lost a neutron but gained a proton)
- atomic number increases by 1 (because it has one more proton)
- forms a new element (because the number of protons have been changed)
What is an isotope?
-different forms of the same element, which have the same number of protons but different numbers of neutrons
